Provide support for playing .mkv on firefox and other browsers without .mkv support

Inspired by the discussion today in
- https://github.com/NeurodataWithoutBorders/nwbinspector/issues/669
- https://github.com/dandi/dandi-archive/discussions/2732
and triggered by @h-mayorquin request, checked on firefox 140.8.0esr (64-bit) on Debian on

https://datasets.datalad.org/repronim/ReproTube/web/#/channel/ReproNim/video/jzPISfLsaPo?tab=local&wide=1

to get

so that might explain why some folks, I believe including my kid, complained that "video did not play".

So I guess we need to explore for some frontend support for that package format as codecs inside are likely to be supported