Provide static API documentation

[laurenty]

It would be nice if the site for ghapi provided browsable/searchable documentation. I understand that the documentation is supposed to be available using Jupyter Notebooks, but for users that aren't familiar with it this is just another obstacle. Also, the site mentions:

To open any page as an interactive notebook in Google Colab, click the Colab badge at the top of the page.

I could not find a Colab badge anywhere...

Thanks!