Contributor Workflow & Permissions

[iqbalcodes6602]

• [P1] Allow contributors to:
  • Upload new problems or read-only content with admin repo access
  • Link newly uploaded problems with specific courses
• [P1] Allow contributors to remove problems/lectures from a course (without deleting them)
• [P1] Upgrade the Python Version for the environment in being used in the repository scripts for Github Actions.