enhancement: frequently asked questions doc

[jamesturner246]

An FAQ-style doc to be distributed with the pre-course prep materal. Will grow as needed.

Some initial points:

• master vs main branch issues
  • note on changing name of existing branch
  • note on setting default branch name with git config --global init.defaultBranch main
• Windows authentication
  • no need for PAT key
  • error 403 on push means auth error
  • if no prompt to enter username/password, then git is using windows credential managet (see below)

If error 403, and Windows is using credential manager, then go to control panel -> credential manager -> windows credentials and delete entry for github.com. The user should then be prompted for user/pass on next push.