REQ - Provide more detailed guidance on setting up GitHub SSH keys

[JFix89]

The pre-session checklist for PHS in-person training contains a link to the Knowledge Base steps on GitHub setup, however there have been issues around getting participants set up with SSH keys that have prevented some from participating in practical elements of the training. Certain participants have also fed back that the Knowledge Base guidance is confusing.

Describe what you'd like
Revise the existing Knowledge Base and expand it to include guidance on setting up SSH keys (i.e. RSA keys) for working with GitHub.

[Moohan]

I just wanted to highlight a guide I wrote for the LIST team - set-up-GitHub.md it goes through the one-time-only steps, including ssh keys, that are required before using git / GitHub. I send it to folks to work through before doing git training etc.