Automate release process

[pdil]

Changes

• Added automated release workflow to step through most of https://github.com/pdil/usmap/wiki/🚀-Release-Process
  • Once active, this will allow most of the manual release work to be performed and added to an automated pull request.
  • The pull request will allow maintainers to review changes and release the package without having to do all of the required steps.
  • The pull request will include pre and post release checklists to ensure all steps are performed.
• Added spelling check

Notes

• The changes in this pull request are non-destructive and do not actually submit the package to CRAN so it can be tested freely.
• This pull request must be merged before it can be tested since it uses a workflow_dispatch workflow.
• After merging, a new pull request will be opened with any ongoing fixes required to make it fully functional.