feat: add tray icon

Author: tymmesyde

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "build-aux/flatpak/flatpak-builder-tools"]
 	path = build-aux/flatpak/flatpak-builder-tools
 	url = https://github.com/flatpak/flatpak-builder-tools
+[submodule "build-aux/flatpak/shared-modules"]
+	path = build-aux/flatpak/shared-modules
+	url = https://github.com/flathub/shared-modules