Temper when full demo runthrough is executed on PRs

[chadwcarlson]

Currently: each push to PR going into main

Suggestions:

• when label is added
• only on this repo id (no forks)
• only delete project if previous steps succeed?

[chadwcarlson]

Add a comment on which label needs to be added to a PR to run tests

https://github.com/marketplace/actions/comment-pull-request