A working question-generation system.

[nghtctrl]

This PR improves on previous PR:

• Now it uses Huggingface pipeline (with GPU support)
• Removed unnecessary and irrelevant operations
• Removed unnecessary pytorch specification from dependencies list
• Some minor refactoring and renaming
• Made thoughtful changes to README with some contribution guidelines
• And more... (minor changes)

This PR adds new features:

• FastAPI back-end now handles CORS mechanism
• FastAPI back-end now handles POST and GET requests, and provides API for it for the front-end

This PR can be improved (future directions):

• Persistent database setup (for storing paragraphs and questions data)
• Performance improvements
• And much more... (e.g. REST API)

This PR needs review, since I will be missing some details; however, I hope this PR is good enough to be merged so that other people can contribute to it as well. Thank you!