Add Licence(s)

[Teque5]

There are lots of audio/video test repositories around and generally they either have a global or per-file license clearly stated.

I suggest CC0 but I don't know the license considerations of the files we already have.

Example Media Codec Repositories

• https://media.xiph.org/
• https://samples.ffmpeg.org/
• https://kodi.wiki/view/Samples