Refactor / Create new documentation page

[carlobortolan]

Is your feature request related to a problem? Please describe.
Current tumlive documentation misses some tumlive features, doesn't match the tumlive UI and could benefit of a re-styling and update.

Describe the solution you'd like
A modern, clean and up-to-date documentation (e.g., using something similar to docusaurus) that contains all relevant information and guides for lecturers or new users.
The "new" documentation could also include a section for new developers, that helps setting up and running all tumlive-related services (as the current GitHub README only includes the Main API, DB and Worker).

Describe alternatives you've considered
Cleaning up / updating the current docs.

Additional context

1. This issue would be worked on as part of the Open Source Lab.

2. Example of how this could look like