[Feature Request] support opening webm files

[mae-pegors]

No description provided.

[HubKing]

I came here for the same thing, and it seems that in the front page, where there are CLI examples, WEBM is used, so the app must actually support WEBM. Is it a GUI bug that it says "Couldn't open that file" when I try to open a WEBM in the GUI?

WEBM is the default format of Gnome's screen recording, which I often need to convert to GIF, because web forums only allow basic image formats, not WEBM.