Add stalebot to help the marking of PRs

[macgills]

Summary:

With the volume of PRs it is easy for some to fall through the cracks. With stalebot we could get a notification if there has been no activity for X number of days. Personally in the past I have used 7 days, issued a warning that the next stale marking will result in closing of the PR and then closed it after a total of 14 days inactivity

[misaochan]

I'm OK with using stalebot for PRs (probably not for issues). I guess a more suitable number of days of inactivity for our repo would be more like 28 (so warning after 21 days and closure after another 7?).

[macgills]

I don't think you can have it go 28-7 automatically. My flow was, stale 7 days>automatic comment and labelling stale> I comment which automatically removes Stale label> 7 days of inactivity reapplies stale label>I close

So I think we would want to choose 17 days then as the stale interval? Or a 3/4 stale strike policy

[Rishavgupta12345]

@nicolas-raoul I want to work on this issue please assign me

[nicolas-raoul]

As we lack reviewers, some reasonable PRs have been sleeping for much more than 14 days. I don't see it as a problem, we review PRs when we have time :-)