Add a recurring GitHub job to clean up issues which need revisions

[jeremystretch]

Proposed Changes

Employ the close-stale-issues GitHub action to automatically remind posters about issues that need further revision, and close out those that have not received any follow-up response. This can be implemented by largely copying the current workflow for stale issues and adjusting the timers & messaging appropriately. My proposed timers are below, but these are up for debate.

• After one week has passed with no updates, post a reminder message that additional information is needed for the issue to progress.
• If no further information has been provided after two weeks, automatically close the issue. (If the author returns in the near future and provides the requested details, the issue can be reopened.)

Justification

Our current issue triage policy contains several paths that end with applying the revisions needed status label to an issue, but does not specify any mechanism for ensuring that those issues are revisited. I try to review these issues occasionally but they often turn stale. Introducing the automated workflow described above will remind people who have submitted issues that need further attention, and automatically close issues which have been abandoned.