Implement Driftwood AppImage manager - Phases 1 and 2

src/config.rs

@@ -0,0 +1,3 @@
+pub const APP_ID: &str = "app.driftwood.Driftwood";
+pub const VERSION: &str = env!("CARGO_PKG_VERSION");
+pub const GSETTINGS_SCHEMA_DIR: &str = env!("GSETTINGS_SCHEMA_DIR");