Feature: Add stale option

[a0m0rajab]

It would be great to have an option to remove the assignee if they did not open a PR or did not comment on the issue for a specific period of time. This would automate some part of the triage team.

[nickytonline]

I think we could after a week (amount of days could be configurable) comment on the issue saying, "user X, are you still working on this?", and then if no activity from them say a week later, we could comment and unassign them.

[koppor]

Just a note: This feature is supported by the assign-issue-action.