docs: fix build of readthedocs
docs: fix build of readthedocs

readthedocs uses Sphinx which loads modules into the python interpreter
to extract docstrings. Consequently one must have all dependencies
installed for the loading to work. A few modules were missing which is
now fixed!

Fixes #754.

plajjan/NIPAP,SpriteLink/NIPAP,bbaja42/NIPAP,SoundGoof/NIPAP,SoundGoof/NIPAP,garberg/NIPAP,garberg/NIPAP,plajjan/NIPAP,fredsod/NIPAP,fredsod/NIPAP,fredsod/NIPAP,SpriteLink/NIPAP,SpriteLink/NIPAP,fredsod/NIPAP,plajjan/NIPAP,SoundGoof/NIPAP,SpriteLink/NIPAP,garberg/NIPAP,fredsod/NIPAP,bbaja42/NIPAP,SoundGoof/NIPAP,ettrig/NIPAP,SoundGoof/NIPAP,bbaja42/NIPAP,bbaja42/NIPAP,plajjan/NIPAP,fredsod/NIPAP,garberg/NIPAP,ettrig/NIPAP,ettrig/NIPAP,garberg/NIPAP,bbaja42/NIPAP,SoundGoof/NIPAP,ettrig/NIPAP,ettrig/NIPAP,plajjan/NIPAP,plajjan/NIPAP,garberg/NIPAP,bbaja42/NIPAP,SpriteLink/NIPAP,ettrig/NIPAP,SpriteLink/NIPAP