The file search box currently offers various parameters, one of them being the particular file extension.
But in many cases this is suboptimal because, instead of looking for .mp4 + .ogv + .mpg + .mov we are more often interested in video/*.
Same for text/*, image/*, audio/*, application/*, …
These are the mime types, using them for search would be easier for the end users and there is a Go module for that