Fix git and github lesson

My git and GitHub lesson was somehow mistakenly attributed to The Hacker Within. See the original at https://github.com/swcarpentry/boot-camps/tree/master/version-control/git/git-and-github. I've removed it from thw-git and re-added it in misc-git/git-and-github. I'm not totally sure how the header yaml is supposed to look but I made my best guess.

This is the downside of copying material without bringing history: you lose the definitive record of authorship. :pensive: