Add VP9 as a valid HLS format to enable remuxing. This is useful when audio processing is required, but the VP9 video can be passed as-is to avoid unnecessary video transcoding.
No VP9 encoder is enabled and should not be enabled. AV1 and HEVC should be preferred over VP9 if video transcoding is required.
Signed-off-by: gnattu <gnattuoc@me.com>