Links redirect in GitHub foundations "cloning and forking"

[bl-freeman]

Both reference links in the cloning and forking chapter of GitHub foundations are out of date and now redirect to the main GitHub community page. While I haven't been able to find a valid link for either, I was able to locate both of the original resources via Wayback Machine. New links to these references should be added, or else replaced with working links to similar resources.

Reference 1: Cloning vs. Forking
Reference 2: What the Fork?