FFmpeg 6.1 support

[AdrianEddy]

This PR adds support for FFmpeg 6.1

[fcfangcc]

Have the same needs and hope to merge them as soon as possible @zmwangx

[Polochon-street]

Hi,

Thank you so much for taking care of this 🙏

Would it be possible to also add CI support? Either directly with ffmpeg_version, either doing the hacky method here 7d08e28 if it doesn't work

[AdrianEddy]

Sorry, I have no idea how to fix that build, apt keeps giving the error about unmet dependencies, I tried everything and it just won't install ffmpeg. ppa:savoury1/ffmpeg6 says 6.1 available there, but it's not working
The docker image is not available yet in jrottenberg/ffmpeg (jrottenberg/ffmpeg#382)

[Polochon-street]

alright, I found a PPA with ffmpeg6.1, we'll use that in the meantime - I cleaned up a bit and will merge #65, it contains the commit you authored, that I slightly tweaked for the CI to work.
I'll release it now, and then we can go ahead with rust-ffmpeg itself.
Thanks again!