Add direct VRM uploads

[SaracenOne]

Depends on #18, allow users to upload VRM files directly to the server and have the server automatically convert them into working V-Sekai avatars.

[SaracenOne]

The conversion step might not be necessary soon, since we plan to allow runtime loading of unmodified VRMs

[fire]

If you just wanted to upload a VRM/GLB directly to the web service, that probably won't be too difficult. The challenge would be getting it to show up in the game. The two paths are backend conversion, or runtime loading. Speaking personally, I would prefer runtime loading, but I understand that's challenging

1. backend conversion
2. runtime loading

[fire]

We don't think that backend conversion or runtime loading is a high priority because editor upload is already working and relatively well.

It was told to me that a major factor in another platform's demise is heavy weight servers.