[TODO] Fileformat handler(callback) API support

[syoyo]

Provide Fileformat handler(callback) API to load custom dataset in user-side

Fileformat is basically determined by file extension.

FileFormat API

• [x] Initial FileFormat API https://github.com/syoyo/tinyusdz/blob/9296b0c3d20592e7b4b69919cf79341182fa971b/src/asset-resolution.hh#L280

Built-in file format

Geometry, Material

• [x] USD: usd, usda, usdc, usdz
• [ ] MaterialX: mtlx https://github.com/syoyo/tinyusdz/issues/86
• [ ] Wavefront obj: .obj (usdObj)
• [ ] FBX? (usdFbx)

Texture(image)

• [x] jpeg, png, bmp, tga and other 8bit LDR images: through stb_image
  • [x] 16bit PNG
• [x] oiio .tx(tiff), tiff, dng: tinydng
• [x] EXR: tinyexr

Audio

• [x] wav, mp3, flac: dr_wav
• [x] alac: alac lib

[syoyo]

Initial FileFormat API is now here:

https://github.com/syoyo/tinyusdz/blob/9296b0c3d20592e7b4b69919cf79341182fa971b/src/asset-resolution.hh#L280

And initial FileFormat example is at

https://github.com/syoyo/tinyusdz/tree/dev/examples/file_format