AV1 video support (external video player integration)

[yeehi]

Could Lagrange support AV1 video?
At the moment, the default behaviour is to open links to such content in a different browser.

https://av1.webmfiles.org/#
https://aomedia.org/av1/

[skyjake]

At least for the time being, I feel that video playback is too complex to be an integrated part of the application (too many commonly used codecs, HW support, multiple new dependencies, platform-dependence, etc.). In these cases I think it's better to rely on separate specialized apps or the platform's video playback features. Currently there isn't even support for animated GIFs (#183).

What could be done instead is to recognize more video formats and do a tighter integration with specific external players like mpv.