add automod action

[jbhannah]

automatically close and lock prs that change more than a single line.

[jbhannah]

gonna do a second take using https://github.com/vloddi/changed-lines-count-labeler to label prs with >= 2 lines changed as spam, and a workflow to close and lock prs/issues with https://github.com/dessant/repo-lockdown when the spam label is added to them.

[madrobby]

@jbhannah note that it's possible that there's more than one signature in a PR e.g. effc2b9

[jbhannah]

@madrobby fair point, but i think it's a reasonable restriction to put in place that each signature be its own commit, for the sake of making it easier to keep bad actors out. otoh, should be ok to bump the limit to 2 signatures in one pr without decreasing effectiveness.

[madrobby]

@jbhannah yeah, agree. (we should check closed PRs occasionally if we missed something; I guess it's sort of like a spam filter in email.)

[Floppy]

Typical that while you're working on this we get our first double-signature PR 😆

Anyway, this looks really helpful, it's much appreciated.

[jbhannah]

deleting unhelpful comments because i find it personally hilarious btw

[drewcassidy]

could lock PRs that delete any lines, since any signatures should be append-only

[shkm]

Currently failing due to lack of permissions; I suspect this will resolve it.

[Floppy]

... did this PR just close and lock itself? 😆

[jbhannah]

lmaoooooo i guess that means it works 🤣

[jbhannah]

um

…ok so i'm gonna merge and push this to trunk manually

[Floppy]

🤣