Update README and mirrors for working build

What is your Merge about?

If this is your first merge, please use the Initialization Template.

Update README for users and update mirrors since build was failing

For more information please visit Iron Bank Documentation #4 (closed) #3 (closed)

Note: Please be sure you create an issue related to this merge request and the issue is labeled ~"Hardening::Review", this will initiate a CHT member review of your merge request.