Add basic e-learning functionality

This is ambitious, but add basic e-learning functionality, including: Lessons, Courses, Enrollment and tracking progress.

Then add a short course like 'Getting started contributing to Open Source.'

The following course does similar, so we could potentially use it for guidance: https://www.udemy.com/course/ruby-on-rails-6-learn-20-gems-build-an-e-learning-platform/