YUV formats

This crate implements conversions from YUV/YCbCr formats to RGB. It also contains enums/constants for describing color spaces common in video formats.

Currently it's in an early stage, implementing subset needed for decoding AV1/AVIF.

Implemented

• [x] Matrix conversion for BT601, BT709, FCC, BT470BG, SMPTE240
• [ ] YCgCo (untested)
• [x] Identity pass-through (GBR)
• [x] Studio and full range colors
• [x] 8-bit, and 10/12 to 16-bit conversions

Planned

• [ ] Gamma conversion
• [ ] Color primaries conversion
• [ ] Chroma upsampling
• [ ] RGB to YUV conversion
• [ ] YUV pixel convenience functions, like in rgb
• [ ] 8-to-16-bit expanding conversion
• [ ] HDR to SDR conversion?
• [ ] Maybe HDR support?