Improve loading speed of desktop app (#4865)

# Description of Changes
Improve loading speed of desktop app by loading a default config until
the backend has spawned.

frontend/src/desktop/config/defaultAppConfig.ts

@@ -0,0 +1,10 @@
+import { AppConfig } from '@app/contexts/AppConfigContext';
+
+/**
+ * Default configuration used while the bundled backend starts up.
+ */
+export const DESKTOP_DEFAULT_APP_CONFIG: AppConfig = {
+  enableLogin: false,
+  premiumEnabled: false,
+  runningProOrHigher: false,
+};