dexc-desktop: flatpak and snap distribution

[peterzen]

This is a tracking issue for the work being done on packaging the desktop app in flatpak and snap, and publishing these on Flathub and the Snap Store (thus also the GNOME Software Center), respectively. The effort is covered in the Decred DEX - Desktop App and Packaging prop.

Snap

• Implement package manifest, configuration and AppStream metadata dexc-desktop: Snap package #2580
• Sandbox compliance changes in dependent libs (dcrd #3196)
• GH build/publish workflow (PoC Snap Store submission
• dexc-desktop sandbox compliance changes - solve the DBus permission required by the fyne systray module
• Test desktop integration aspects under GNOME/KDE and other major Linux desktop environments
• Finalize and polish app metadata - expand on introductory copy for the app stores and create high quality screenshots/featured banner
• Store submission

The latter 2 is best done after the rebrand is complete so as to avoid having to go through the submission/request process twice.

Flatpak

• Implement Flatpak builder and repo
• Test desktop integration aspects under GNOME/KDE and other major Linux desktop environments
• Create Decred flatpak repo (self hosted repository similar to our Umbrel Community store) and scripts/GH workflow to push updates
• Finalize and polish app metadata (shares assets with those created for Snap)
• Make build process compliant with Flathub requirements, i.e. vendoring Go libraries as the build process must run in a network isolated sandbox
• Create Flathub store submission

As with Snap, the store submission related items should ideally happen once the rebrand has been completed, although Flathub is less finicky than Snap about resubmissions under a different brand.

[exitus1]

Going to bump this...it's free advertising for Bison Wallet and could come up with anyone that searches "Bitcoin"