Support .mkv video format

[lulzsun]

Commit 7c8f627 allows for users to add .mkv video files to view in the video player.

However, this does not fully implement support for .mkv files.

Some of the following changes will need to be done in order for full .mkv support:

• Change compressor to support .mkv files
• Change uploaders to support .mkv files
• Create a user setting to change output file format (.mp4, .mkv)

[lulzsun]

Optionally, also support fragmented .mp4 since we are now on OBS 29.1.1.

Benefit of .mkv and fragmented .mp4 is for whenever recording gets interrupted/corrupted, there would still be a chance to recover the capture.