CI: Automatically add labels for new PRs and issues

While the effort to add labels for each PR and issue is tiny, it adds up over time. It would be great to do this automatically based on the tile of the PR.

Example CI script to assign labels to issues:

https://docs.github.com/en/actions/tutorials/manage-your-work/add-labels-to-issues

Example command to edit labels on PRs:

`gh pr edit 23 --add-label "bug,help wanted" --remove-label "core"`