octant-desktop: init at 0.18.0

[06kellyjac]

Motivation for this change

octant-desktop: init at 0.18.0
Unpacked from an AppImage or dmg depending on the platform

Based on the joplin-desktop package, thanks @HugoReeves

I've done a nix-env -f . -iA octant-desktop install and the icons and launch works fine in my rofi launcher
The starboard octant plugin I have installed to ~/.config/octant/plugins also works well

I've done a build of the dmg version on NixOS and the structure looked alright.
Probably worth installing on an x86 mac to test it.

I've made sure that the "binary" for the app-image is called octant-desktop so that it doesn't clash with the cli copy of octant

Also:

octant cleanup

• Remove unneeded quotes around ${system}
• Cleanup meta
• Correct the variable names in update.sh
  • Luckily even though the names were a jumble the correct shas were being put in the right places

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[06kellyjac]

Result of nixpkgs-review pr 117677 run on x86_64-linux 1

1 package built:

• octant-desktop