Improve appstream metainfo

[bertob]

This app's app store listing has a lot of potential, but there are a bunch of smaller papercuts:

• Summary is longer than 35 characters #249
• Screenshots with non-default window controls (should be close-only) #228
• The description GTK4 Discord client in Go is a bit short, it'd be nicer to at least have a full sentence listing the most important features (or in this case maybe also which Discord features are not supported yet)
• No release notes (at least not in GNOME Software)
• Flathub verification #261
• Brand colors

[tfuxu]

For screenshots with non-default controls, I created #228 a while ago. Also, you can add the lack of specified branding colors to the list.

[diamondburned]

Tracking comment:

• [x] Summary is longer than 35 characters Better appdata summary #249
• [ ] Screenshots with non-default window controls (should be close-only) Screenshots should use default settings #228
• [x] The description GTK4 Discord client in Go is a bit short, it'd be nicer to at least have a full sentence listing the most important features (or in this case maybe also which Discord features are not supported yet)
• [ ] No release notes (at least not in GNOME Software)
• [x] Flathub verification Flathub Verification #261
• [ ] Brand colors

[diamondburned]

Where does the brand color go? Are they more for the UI or for the metadata?

[bertob]

Opened a PR for brand colors, for context, this is what that's about: https://docs.flathub.org/blog/introducing-app-brand-colors

[tfuxu]

Nice, we are currently only failing the "Default settings" check in Flathub: