Sure thing!
Tutorials go into this repository:
https://github.com/openframeworks/ofSiteTake a look at the other tutorials in the _tutorials folder to see how it's done.
regarding markdown, there's some info in the ofSite repo readme, and the ofsite repo wiki, and the infor already posted in this thread.
regarding git(hub), there's a tutorial about that here:
http://www.openframeworks.cc/tutorials/developers/002_git_and_openFrameworks.html and some more advanced stuff here:
https://github.com/openframeworks/openFrameworks/wiki/openFrameworks-git-workflow