Adding two themes to the list

[choldgraf]

It was a bit hard to figure out exactly how the themes were meant to be ordered, so hopefully I got it right 😬

[pradyunsg]

I'm a bit surprised that no one noticed, but this PR broke sphinx-themes.org. :)

https://github.com/sphinx-themes/sphinx-themes.org/commit/51f23299faae1e5e13719946b39c875f3445634a should fix things tho.

[choldgraf]

oops, what did I do?!

[pradyunsg]

You shook a Jenga tower. :P