Add a TODO mechanism / file

[jcraigk]

Rubocop is a linter for checking the style/formatting of Ruby code. It has a file called .rubocop_todo.yml that tracks known violations of rules. For a large codebase that has been touched by many engineers, it's a great way to specify areas of the system that need attention, but that are not immediately prioritized for fixing. Something similar in Woke would be a nice addition. This would expand on the functionality of .wokignore, allowing automation tools like Danger to highlight known issues in Pull Requests while still continuing to truly ignore entities specified in .wokeignore.