Some stale bot

[yajo]

Actual Situation

Copier is growing. Luckily not so often, some people come, open a PR, and abandon it. However, sometimes it does happen.

A big amount of open issues and PRs limits the quality of support that we can give to active and important ones.

Desired Situation

A nice bot could mark as stale and, later, close issues and PRs before they rot.

Proposed solution

Use https://github.com/marketplace/actions/close-stale-issues which is just a CI that runs every week and passes a 🧹 across the repos.

[pawamoy]

Might make sense for PRs, but I'm not a fan of bots staling/closing valid issues or feature requests.