Support MP4 (and possibly other formats) videos

[Xottab-DUTY]

Is your feature request related to a problem? Please describe.
Support .mp4 videos (in addition to .ogm).

Describe the solution you'd like
Use ffmpeg library to add support for .mp4 and possible many other formats.

Describe alternatives you've considered
It's possible to use gstreamer for that purpose.

Additional context
I had this idea long ago, and after Enhanced Edition (#1865) release it's even more relevant.

Good idea, it will be easier to add custom videos for the game. I once tried to upscale them using a neural network, but I couldn't convert them to OGM without bugs.