Add workflow to close stale issues and PRs

[derrix060]

Introduce a GitHub Actions workflow to automatically close stale issues and pull requests. This helps maintain repository hygiene by reducing clutter from inactive items. The workflow marks issues as stale after 60 days of inactivity and closes them 14 days later if no further activity occurs.

The issues and PRs that have a milestone assigned will not be looked at by the bot. This means that it is still possible to plan work that won't be worked for some time