FR: Ability to add predicates or add certain extensions to existing predicates

[dmt-hub]

Would be nice if we could add new predicates via the preferences file or add extensions to predicates.

For example the predicate:
Archive - would like to add .rar & .7z to it.
Audio - .flac. / m4a / .ogg / .opus / etc..
Video - .mp4 / .mkv

Thank you!

[dmt-hub]

A predicate called EXTENSION or TYPE (->filetype) would be interesting.
We can fill in: EXTENSION opus or TYPE opus for example - which would then show all .opus files on the system.