Fix AppStream developer id

[musicinmybrain]

Per https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-developer, this should have been org.pencil2d instead of pencil2d.org. Technically, the ID can be any string, but the FreeDesktop documentation strongly recommends a reverse-DNS string.

This is a follow-up to #1796.

[J5lx]

Well spotted, thanks for fixing that. I just wish those AppStream folks would just pick a naming scheme and stick with it – until just three weeks ago they still recommended a web URL instead. Same with the app id, back when we picked ours all of their examples had mixed-case component ids, now they explicitly recommend lower-case.

But anyway, that’s AppStream’s fault, not yours. Sorry for the little rant and thanks for the PR!

[musicinmybrain]

Thanks for the quick review!

I agree, even as a downstream packager, the recent churn in the AppStream XML format and the way new warnings keep popping up that cause validation failures on previously-valid files has been a pain to keep up with. (AppStream 1.0.2 started warning when <developer/> has no id, so at least we were ahead of the game there.)

I hope things are starting to stablilize now!