GitHub project workflows

[ddabble]

Proposed changes

Added GitHub Actions workflows for automatically adding issues and PRs to the repo's project and setting adequate "Status" and "Date posted" values.

Areas to review closely

None in particular, as these workflows have already been tested in a since-deleted repo.

Checklist

(If any of the points are not relevant, mark them as checked)

• [x] Created tests that fail without the changes, if relevant/possible
• [x] Made sure that your code conforms to the code style guides and that any common code smells have been addressed
  • (It's not intended that you read through this whole document, but that you get yourself an overview over its contents, and that you keep it in mind while taking a second look at your code before opening a pull request)
• [x] Added sufficient documentation - e.g. as docstrings or in the README, if suitable
• [x] Added your changes to the "Unreleased" section of the changelog - mainly the changes that are of particular interest to users and/or developers, if any
• [x] Added a "Deployment notes" section above, if anything out of the ordinary should be done when deploying these changes to the server

[ddabble]

Merging without approval, as these changes have already been tested fairly thoroughly in a since-deleted repo, and because there are currently no other people in the Dev committee who have experience with writing GitHub Actions workflows 😅