Simplify prereqs

[richelbilderbeek]

The prereqs are needlessly detailed.

Can we/I simplify?

I suggest to simplify by:

• [x] #20
• [x] Assume learners know git: only link to other sites
• [x] Only link to VSCode, git terminal and GitHub
• [x] Do add: how to verify each of these things work
• [ ] Remove using SSH keys for git: it is clever, yet not a goal of the course

I volunteer to do these

[bclaremar]

Kept ssh keys otherwise making clearer