93219: Support Router in InitService

For Router to work properly, APP_BASE_HREF must be resolved _before_ the APP_INITIALIZER factory is called (otherwise Angular will attempt to initialize APP_BASE_HREF too soon)
To fix this we add a pre-initialization hook to APP_CONFIG so BrowserInitService can resolve it before APP_INITIALIZER

src/config/app-config.interface.ts

@@ -36,6 +36,10 @@ interface AppConfig extends Config {
   mediaViewer: MediaViewerConfig;
 }
 
+/**
+ * Injection token for the app configuration.
+ * Provided in {@link InitService.providers}.
+ */
 const APP_CONFIG = new InjectionToken<AppConfig>('APP_CONFIG');
 
 const APP_CONFIG_STATE = makeStateKey('APP_CONFIG_STATE');