You can make it static because you are returning a static member. It means that you should probably return by const reference (even if I do not remember if it is always the best answer).

I had it this way before, but actually reverted it to make it consistent with the plugins, and this would also allow to potentially change the implementation later, wouldn't it? Anyway, your call.

The "read" is supposed to mark that only read operations for these mimetypes are supported. I plan to add support for writing add some points, and the supported formats may differ.
Or maybe one could use extractionMimeTypes() ?