add KTX2/Draco loader to avatar-editor

[kira924age]

✅ Closes: #6209

I add KTX2/Draco Loader to avatar-editor.js.
Now we can upload KTX2/Draco glb file from avatar upload page.

Screenshot

Screencast.from.2023-08-14.12-39-52.webm

[Exairnous]

It's great to see Draco support for avatars being added, but I thought KTX2 support was already present. I'm pretty sure I have created and uploaded an avatar with KTX2 texture compression to Hubs.

[kira924age]

@Exairnous

Thank you for your comment. As you pointed out, I was able to upload the avatar using the KTX2 Texture even after removing the "setKTX2Loader" process. In this scenario, it seems that there is no need to call setKTX2Loader, so I have removed it. Perhaps in this case, only the uploading is being performed, and the texture loading might not be taking place.

[Exairnous]

Perhaps, but I do see textures in the preview window with a KTX2 avatar, so not sure. Glad I could help anyway.

[keianhzo]

KTX2 is used when rendering the model in the scene and in the avatar preview viewport (both via gltf-model-plus.js loadGLTF) but not during the uploadAvatar` step in the editor. The loader seems to be crashing only for the Draco extension and not for the Basis one, not sure why but I don't think we need to add the KTX2 loader as that extension is available when loading for rendering later.