ci: replace auto-ci with commands

[dshemetov]

Checklist

Please:

• Make sure this PR is against "dev", not "main" (unless this is a release
  PR).
• Request a review from one of the current main reviewers:
  brookslogan, nmdefries.
• Makes sure to bump the version number in DESCRIPTION. Always increment
  the patch version number (the third number), unless you are making a
  release PR from dev to main, in which case increment the minor version
  number (the second number).
• Describe changes made in NEWS.md, making sure breaking changes
  (backwards-incompatible changes to the documented interface) are noted.
  Collect the changes under the next release number (e.g. if you are on
  1.7.2, then write your changes under the 1.8 heading).
• See DEVELOPMENT.md for more information on the development
  process.

Change explanations for reviewer

• move style, lint, document, preview-docs all in pr-commands.yaml
• all are now triggered with PR comments, instead of auto-running
• update PR template to remind user to run these commands

Magic GitHub syntax to mark associated Issue(s) as resolved when this is merged into the default branch

• Resolves #{issue number}

[dsweber2]

Do we have these set up as optional in e.g. epipredict? Or is this a first

[dshemetov]

Yes cmu-delphi/epipredict#453

[brookslogan]

This seems like it's going to remove a lot of annoyance! See potential todo in inline comments.