[Feature Request] Add MKV Support

[adworacz]

Echoing this Doom9 user: https://forum.doom9.org/showthread.php?p=1915756#post1915756

Please add support for MPEG2 in MKV. Especially with the proliferation of MakeMKV usage, particularly on Linux, many DVDs are being bundled up as MKV files out of the gate.

As called out in that same thread, FFMS2 has issues with MPEG2 (I've seen it myself in a few of my own clips). L-SMASH seems slightly more reliable, but a proper D2V index seems the best option.

Please and thank you for your efforts!