Add support for newly-added track flags
A few track flags have recently been added to the spec:
- Three for accessibility services: https://github.com/ietf-wg-cellar/matroska-specification/commit/0e330fded85654d637c256797ea9cc6bfb79fde3
- Hearing-impaired (for e.g. subtitle tracks with text describing non-dialogue sounds)
- Visual-impaired (for e.g. descriptive audio service)
- Text descriptions (for subtitle tracks with text containing descriptions of video content, for TTS or braille systems)
- Original-language: https://github.com/ietf-wg-cellar/matroska-specification/commit/282bfa742eb1c6d5c5a51cb758a13c2e5ec0c59b
- Commentary: https://github.com/ietf-wg-cellar/matroska-specification/commit/a59bfc4255391d39d7f0a897543610000fe31c1e
I'd imagine these will want support similar to that of the default and forced flags.