Convert image-style cannot convert GIF to WEBP (Lost animation).

RTBC for patch at #6.
Also, to get this to work, don't forget to activate the "-coalesce" option in the advanced settings (not really sure why this is not activated by default in the module?)

I do not think this is the right way to address this. It would introduce a behaviour change vs current state where only the first frame is converted for animated GIFs. We might argue whether the current state is the right one or not, but no matter what we cannot simply change the behaviour like this.

I'd rather go a path similar to #2786435: Support '-coalesce' of Animated GIF image files → where a configuration setting was introduced for the purpose. So each site owner to decide.

We also need tests.

thanks @internetter but patch#6 doesn't work for me.
i've created new patch. also checking "-coalesce" option which can be apply to gif and webp destination format.

trackleft2 → changed the visibility of the branch 3295470-convert-image-style-cannot to hidden.

The patch from #10 works for me, I've create a merge request with the patch so we can continue work on this.
Changing to Needs work, because the maintainer said this needs tests.

I've added a PHPUnit test

Manually triggered the "tests only" pipeline on the MR and saw that the new test added passes even without the other MR changes which I don't think is the expected result.

Spoke to @trackleft2 about this on Slack and he mentioned that he thinks he needs to add something to the test that verifies the generated file is still actually a multiframe image.