v1.12.0 - MIAF conformance / premultiplied alpha
- check for MIAF conformance and add as compatible brand
- signaling of premultiplied alpha
- parse AV1
obu_sequence_header
forav1C
box - write
pixi
box in AVIFs - save alpha as monochrome in AVIF if possible
- many build fixes (thanks to the numerous external contributors)