Documentation: Update README and CONTRIBUTING (#1199)

Simplify `README` in an effort to highlight what really matters, and
remove references to each generator.

Instead, we introduce `FEATURES.md` which was modified from the `README`
generated by `bin/rails suspenders:cleanup:generate_readme`

Updates `CONTRIBUTING` guide to account for changes in the test suite.
Since this new build was generated from am [engine][], we no longer use
RSpec, and instead use the default test suite.

Remove reference to styleguide since the link is broken, and update link
to Suspenders boy to use HTTPS.

[engine]: https://guides.rubyonrails.org/engines.html

CONTRIBUTING.md

@@ -23,12 +23,16 @@ Run the setup script.
 Make sure the tests pass:
 
 ```
-bundle exec rake
+bin/rails test
 ```
 
-Make your change, with new passing tests. Follow the [style guide][style].
+Make sure there are no linting violations:
 
-  [style]: https://github.com/thoughtbot/guides/tree/master/style
+```
+bin/rails standard
+```
+
+Make your change, with new passing tests.
 
 Mention how your changes affect the project to other developers and users in the
 `NEWS.md` file.
@@ -42,6 +46,17 @@ This is a time for discussion and improvements,
 and making the necessary changes will be required before we can
 merge the contribution.
 
+## Testing Generators
+
+There is a smaller dummy application at `test/dummy`. This application is used
+as a mounting point for the engine, to make testing the engine extremely simple.
+
+There are a number of [assertions][] and [helpers][] that make testing
+generators easier.
+
+[assertions]: https://api.rubyonrails.org/classes/Rails/Generators/Testing/Assertions.html
+[helpers]: https://api.rubyonrails.org/classes/Rails/Generators/Testing/Behavior.html
+
 ## Publishing to RubyGems
 
 When the gem is ready to be shared as a formal release, it can be

FEATURES.md

@@ -0,0 +1,200 @@
+# Features
+
+## Local Development
+
+### Seed Data
+
+- Use `db/seeds.rb` to create records that need to exist in all environments.
+- Use `lib/tasks/dev.rake` to create records that only need to exist in development.
+
+Running `bin/setup` will run `dev:prime`.
+
+### Tasks
+
+- Use `bin/rails suspenders:db:migrate` to run [database migrations][]. This script ensures they are [reversible][].
+- Use `bin/rails suspenders:cleanup:organize_gemfile` to automatically organize the project's Gemfile.
+- Use `bin/rails default` to run the default Rake task. This will do the following:
+  - Run the test suite.
+  - Run a Ruby and ERB linter.
+  - Scan the Ruby codebase for any dependency vulnerabilities.
+
+[database migrations]: https://edgeguides.rubyonrails.org/active_record_migrations.html#running-migrations
+[reversible]: https://edgeguides.rubyonrails.org/active_record_migrations.html#making-the-irreversible-possible
+
+## Configuration
+
+### Test
+
+- Enables [raise_on_missing_translations][].
+- Disables [action_dispatch.show_exceptions][].
+
+[raise_on_missing_translations]: https://guides.rubyonrails.org/configuring.html#config-i18n-raise-on-missing-translations
+[action_dispatch.show_exceptions]: https://edgeguides.rubyonrails.org/configuring.html#config-action-dispatch-show-exceptions
+
+### Development
+
+- Enables [raise_on_missing_translations][].
+- Enables [annotate_rendered_view_with_filenames][].
+- Enables [i18n_customize_full_message][].
+- Enables [query_log_tags_enabled][].
+
+[raise_on_missing_translations]: https://guides.rubyonrails.org/configuring.html#config-i18n-raise-on-missing-translations
+[annotate_rendered_view_with_filenames]: https://guides.rubyonrails.org/configuring.html#config-action-view-annotate-rendered-view-with-filenames
+[i18n_customize_full_message]: https://guides.rubyonrails.org/configuring.html#config-active-model-i18n-customize-full-message
+[query_log_tags_enabled]: https://guides.rubyonrails.org/configuring.html#config-active-record-query-log-tags-enabled
+
+### Production
+
+- Enables [require_master_key][].
+
+[require_master_key]: https://guides.rubyonrails.org/configuring.html#config-require-master-key
+
+### Linting
+
+- Uses [@thoughtbot/eslint-config][] for JavaScript linting.
+- Uses [@thoughtbot/stylelint-config][] for CSS linting.
+- Uses [prettier][] for additional linting.
+- Uses [better_html][], [erb_lint][], and [erblint-github][] for ERB linting.
+- Uses [standard][] for Ruby linting.
+
+**Available Commands**
+
+- Run `yarn lint` to lint front-end code.
+- Run `yarn fix:prettier` to automatically fix prettier violations.
+- Run `bin/rails standard` to lint ERB and Ruby code.
+- Run `bundle exec standardrb --fix` to fix standard violations.
+
+[@thoughtbot/eslint-config]: https://github.com/thoughtbot/eslint-config
+[@thoughtbot/stylelint-config]: https://github.com/thoughtbot/stylelint-config
+[prettier]: https://prettier.io
+[better_html]: https://github.com/Shopify/better-html
+[erb_lint]: https://github.com/Shopify/erb-lint
+[erblint-github]: https://github.com/github/erblint-github
+[standard]: https://github.com/standardrb/standard
+
+## Testing
+
+Uses [RSpec][] and [RSpec Rails][] in favor of the [default test suite][].
+
+The test suite can be run with `bin/rails spec`.
+
+Configuration can be found in the following files:
+
+```
+spec/rails_helper.rb
+spec/spec_helper.rb
+spec/support/action_mailer.rb
+spec/support/driver.rb
+spec/support/i18n.rb
+spec/support/should_matchers.rb
+```
+
+- Uses [action_dispatch-testing-integration-capybara][] to introduce Capybara assertions into Request specs.
+- Uses [should-matchers][] for simple one-liner tests for common Rails functionality.
+- Uses [webmock][] for stubbing and setting expectations on HTTP requests in Ruby.
+
+[RSpec]: http://rspec.info
+[RSpec Rails]: https://github.com/rspec/rspec-rails
+[default test suite]: https://guides.rubyonrails.org/testing.html
+[action_dispatch-testing-integration-capybara]: https://github.com/thoughtbot/action_dispatch-testing-integration-capybara
+[should-matchers]: https://github.com/thoughtbot/shoulda-matchers
+[webmock]: https://github.com/bblimke/webmock
+
+### Factories
+
+Uses [FactoryBot][] as an alternative to [Fixtures][] to help you define
+dummy and test data for your test suite. The `create`, `build`, and
+`build_stubbed` class methods are directly available to all tests.
+
+Place FactoryBot definitions in `spec/factories.rb`, at least until it
+grows unwieldy. This helps reduce confusion around circular dependencies and
+makes it easy to jump between definitions.
+
+[FactoryBot]: https://github.com/thoughtbot/factory_bot
+[Fixtures]: https://guides.rubyonrails.org/testing.html#the-low-down-on-fixtures
+
+## Accessibility
+
+Uses [capybara_accessibility_audit][] and
+[capybara_accessible_selectors][] to encourage and enforce accessibility best
+practices.
+
+[capybara_accessibility_audit]: https://github.com/thoughtbot/capybara_accessibility_audit
+[capybara_accessible_selectors]: https://github.com/citizensadvice/capybara_accessible_selectors
+
+## Advisories
+
+Uses [bundler-audit][] to update the local security database and show
+any relevant issues with the app's dependencies via a Rake task.
+
+[bundler-audit]: https://github.com/rubysec/bundler-audit
+
+## Mailers
+
+[Intercept][] emails in non-production environments by setting `INTERCEPTOR_ADDRESSES`.
+
+```sh
+INTERCEPTOR_ADDRESSES="[email protected],[email protected]" bin/rails s
+```
+
+Configuration can be found at `config/initializers/email_interceptor.rb`.
+
+Interceptor can be found at `app/mailers/email_interceptor.rb`.
+
+[Intercept]: https://guides.rubyonrails.org/action_mailer_basics.html#intercepting-emails
+
+## Jobs
+
+Uses [Sidekiq][] for [background job][] processing.
+
+Configures the `test` environment to use the [inline][] adapter.
+
+[Sidekiq]: https://github.com/sidekiq/sidekiq
+[background job]: https://guides.rubyonrails.org/active_job_basics.html
+[inline]: https://api.rubyonrails.org/classes/ActiveJob/QueueAdapters/InlineAdapter.html
+
+## Layout and Assets
+
+### Stylesheets
+
+- Uses [PostCSS][] via [cssbundling-rails][].
+- Uses [modern-normalize][] to normalize browsers' default style.
+
+Configuration can be found at `postcss.config.js`.
+
+Adds the following stylesheet structure.
+
+```
+app/assets/stylesheets/base.css
+app/assets/stylesheets/components.css
+app/assets/stylesheets/utilities.css
+```
+
+Adds `app/assets/static` so that [postcss-url][] has a directory to copy
+assets to.
+
+[PostCSS]: https://postcss.org
+[cssbundling-rails]: https://github.com/rails/cssbundling-rails
+[modern-normalize]: https://github.com/sindresorhus/modern-normalize
+[postcss-url]: https://github.com/postcss/postcss-url
+
+### Inline SVG
+
+Uses [inline_svg][] for embedding SVG documents into views.
+
+Configuration can be found at `config/initializers/inline_svg.rb`
+
+[inline_svg]: https://github.com/jamesmartin/inline_svg
+
+### Layout
+
+- A [partial][] for [flash messages][] is located in `app/views/application/_flashes.html.erb`.
+- Sets [lang][] attribute on `<html>` element to `en` via `I18n.local`.
+- Dynamically sets `<title>` via the [title][] gem.
+- Disables Turbo's [Prefetch][] in an effort to reduce unnecessary network requests.
+
+[partial]: https://guides.rubyonrails.org/layouts_and_rendering.html#using-partials
+[flash messages]: https://guides.rubyonrails.org/action_controller_overview.html#the-flash
+[lang]: https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/lang
+[title]: https://github.com/calebhearth/title
+[Prefetch]: https://turbo.hotwired.dev/handbook/drive#prefetching-links-on-hover