It is not that hard, an API from a very known source already exists:
https://developers.google.com/translate/
However, I don't see the chess.com staff add anything like this, and considering the size of chess.com, they will have to pay (maybe restrict it to only premium members would be an option).
If this has been covered some time in the past - forgive my ignorance. As I have enjoyed playing the game with others from all over the world, I thought that maybe not everyone is conversant in English. Is it possible that chess.com would look into translation software - I tried to learn French and German (wife's native language) once - not going to happen!