Added stale workflow

[naman9271]

Fixes #1242

This pull request introduces a new GitHub Actions workflow to automatically manage stale issues and pull requests in the repository. The workflow is designed to help keep the issue and PR list clean by warning about inactivity and eventually closing items that have not seen recent activity.

Automation for stale issues and pull requests:

• Added .github/workflows/stale.yml to mark issues as stale after 60 days of inactivity and close them after 14 more days, with custom warning and closing messages.
• Configured pull requests to be marked as stale after 30 days of inactivity and closed after 7 additional days, with separate messages for PRs.

[naman9271]

Hi @joaquinvanschoren , @janvanrijn please review when you get a chance - thanks