types/video: Fix differentiation between Matroska and WebM files
types/video: Fix differentiation between Matroska and WebM files

EBML files can be identified further using the EBML Document Type.

See:
https://www.matroska.org/technical/basics.html
https://datatracker.ietf.org/doc/html/rfc8794#section-11.2.6
https://datatracker.ietf.org/doc/html/rfc8794#section-17.2

h2non/filetype.py