App: use vrm template to load/change different quality meshes for avatars

[0reo]

Currently the Avatar class handles loading different quality vrms and adding/removing them from the scene. Initial vrms based on the users set gfx settings should be provided for use by the Avatar class, and the vrm totum app should be called to control preparing the meshes.

[0reo]

webaverse/totum#78 is a dependency.