Hide request comment as resolved after PR is closed

[JoshuaKGoldberg]

Is your feature request related to a problem? Please describe.

After the PR for a "[@]allcontributors add (username) for (type)" comment has been closed, it'd be nice if the bot hid that comment as resolved. Those comments just sit around and take up space.

It'd also be great if the bot's response comment was hidden as resolved too.

Example comments: user request -> bot response

Describe the solution you'd like

Upon a PR being closed -e.g. when it's merged- use the GitHub API to mark that comment as resolved?

Describe alternatives you've considered

Users can always resolve comments manually, which is what I've been doing. But it's a chore.