[Docs] Fill out ttLib table section. Part of a bottom-up docs rework for ttLib. Note that 23546cf changes the `import`s for ttLib/tables/_g_v_a_r.py to un-confuse autodoc.
[Docs] Fill out ttLib table section. Part of a bottom-up docs rework for ttLib. Note that 23546cf changes the `import`s for ttLib/tables/_g_v_a_r.py to un-confuse autodoc.