Ask for the video language if audio is imported

[prototyperspective]

For videos where audio is imported, please show a textbox with an autocomplete-dropdown for the language. Then an inferrable meta-category for the language like Videos in English could be added, see the other issue about this :#189.

This is useful for better multilingualism-support such as redubbing of high-quality videos into other languages (as done here) and subtitle translations or for allowing for petscan results to show these.

I think there should be a separate dropdown value for "Music" which would add Videos with music (which could later be refined such as by genre and/or source location).