Update Yeoman instructions to include creating GitHub repo as origin

[djbpitt]

Your to-do

Our Yeoman instructions create a local repo with a single branch called master. The conventional name for a main branch is now main; we need to update the instructions to include git branch -m main.

We need to add instructions for creating a matching main branch on GitHub and configuring as origin.

Issues you may encounter

When creating origin at GitHub must tread carefully to avoid unrelated histories.

[gabikeane]

To do on 2022-07-02

[EmmaSchwarz]

Finished on 2022-07-02.