GitHub PR status/assignee

Automatically mark PRs as 'in progress' when opened, add 'needs review' when ready for review
Readme:

Every time someone opens a pull request this sketch will add the In Progress Label (and assign to the person who opened the PR) unless the PR already has the Needs Review Label.

This supports the ethos of GitHub Flow whereby it's common to open a pull request before the code is ready to merge to open discussion earlier, enabling earlier discussion and guidance.

See GitHub: one label of each type for a handy companion sketch and an outline of some labels you might choose to use in your repository.

TODO:

  • Automatically enter "needs review" state when a reviewer is assigned.