In most git frontends there's a bar on repos that indicate which languages are used in repositories and their percentages compared to one another. I forget, but I believe this is usually done by just periodically checking the file extensions; though that's an implementation detail.
Would make me soyface if this were implemented.
Yeah for sure! We want to use https://github.com/go-enry/go-enry for this (when we get around to doing it that is; happy to accept a patch meanwhile!).