PyGithub example usage

Motivation: #862 #456 #321 #584 #762

PyGithub is a great library, however it may not be intuitive to use at the beginning. Not everyone is a Github API expert, so I am trying to provide some working examples (recipes) that will hopefully help you get started.

The skeleton has been setup here and the example docs is already live on readthedocs as usual:

https://pygithub.readthedocs.io/en/latest/examples.html

Note that the list will expand and any PR to add more examples is extremely welcome

If you want to see any examples not covered here, just leave a comment.