Support for WebP image format

[shawn_a]

It would probably be trivial to add it, but we might run into issues of our uploader scripts we use.
We might have to make sure our allowed files list is globalized across the system.

Otherwise I do not see how we could add support, you should be able to use them just fine.
Ckeditor might not support them yet, but that is not something we can control.

But try to find out if you wish. It would be nice to know. We are in dire need of an update to our dependancies.