User login

**Is your feature request related to a problem? Please describe.**
This is a prerequisite for:
- #57 
- #58 

**Describe the solution you'd like**
[Create a GitHub OAuth app](https://docs.github.com/en/apps/oauth-apps/building-oauth-apps/creating-an-oauth-app)

**Additional context**
Reference: https://www.youtube.com/watch?v=rRn2EisxPl4
