Add Git Flight Rules as a resource to Git content

[lizTheDeveloper]

Mozilla engineer @k88hudson created an amazing resource for Git, which would materially improve the git curriculum. It also looks like a great source of insights that we might not have.

https://github.com/k88hudson/git-flight-rules

• Add links to this resource to relevant Git insights (link to specific sections of the resource)
• Create Standards and Objectives for uncovered content from that repo
• Create insights for uncovered content from that repo