generated gtk-doc online

[Colin Walters <walters verbum org>]

In case it's useful, I have uploaded a snapshot of the gtk-doc that
ostree recently gained to:

https://people.gnome.org/~walters/ostree/doc/index.html

I plan to continually migrate content from the wiki into the gtk-doc,
mainly because it's more professional looking than the wiki, and the
wiki lost 20 minutes worth of typing just because I accidentally pressed
the back button.