Reusable Code for Unassign Inactive Issues

[SukhvirKooner]

Summary

This PR introduces a GitHub Action to automatically unassign users from issues that have been inactive for a specified duration.
Manual verification steps performed:

1. Tested the action on a test repository by creating an issue, assigning a user, and letting it remain inactive.
2. Verified that the action successfully unassigned the user after the inactivity threshold was met.
3. Reviewed the workflow logs to ensure proper execution without errors.

No UI changes are involved in this update.

References

• Addresses issue learningequality/kolibri#12837
• GitHub Actions documentation was referred to for implementation.

Reviewer guidance

1. To test these changes, review the .github/workflows/unassign-inactive-issue.yml file for correctness.
2. Simulate the action in a test repository to verify behavior.
3. Ensure that the inactivity threshold and other parameters are set correctly and match project requirements.
4. For Testing purposes inactivityPeriodInMinutes is set to 10 , can be changed in scripts/unassign-inactive-issues.mjs