Linux metainfo file

**What's your use case?**

Hi, I'm hoping to see more support for Linux desktop, and for that an upstream metainfo file is needed.

e.g. https://github.com/flathub/flathub/pull/6904

**What's your proposed solution?**

https://www.freedesktop.org/software/appstream/metainfocreator/#/guiapp

It's quite straightforward to fill in. Further information available here https://docs.flathub.org/docs/for-app-authors/metainfo-guidelines with linters and stuffs. I've made an attempt [here](https://raw.githubusercontent.com/theoden8/orange_unofficial/1ebfbe5aa359331dc2273e3ef08f37fecfd05e6a/io.github.theoden8.orange_unofficial.metainfo.xml) (with correction for affiliation).

The file can be placed in `/distribute/` folder where the icon and .desktop files are located.

**Are there any alternative solutions?**