v0.12.0

What's Changed

• Improve parsing of hdlr and dref boxes by @gBillal in #33
• Add output_structure option to mp4 to annexb filter by @gBillal in #34
• Add support for av1 codec by @gBillal in #35
• Allow sample payload to be iodata by @gBillal in #36
• Add opus boxes by @gBillal in #37

Full Changelog: v0.11.0...v0.12.0