feat: Add loading spinner on card initialization (#1549)

* feat: Add loading spinner on card initialization

* Minor doc fix.

src/card-controller/initialization-manager.ts

@@ -31,12 +31,17 @@ export class InitializationManager {
   // initialization" (above) are followed.
   protected _initializationQueue = new PQueue({ concurrency: 1 });
   protected _initializer: Initializer;
+  protected _everInitialized = false;
 
   constructor(api: CardInitializerAPI, initializer?: Initializer) {
     this._api = api;
     this._initializer = initializer ?? new Initializer();
   }
 
+  public wasEverInitialized(): boolean {
+    return this._everInitialized;
+  }
+
   public isInitializedMandatory(): boolean {
     const config = this._api.getConfigManager().getConfig();
     if (!config) {
@@ -113,6 +118,7 @@ export class InitializationManager {
       return;
     }
 
+    this._everInitialized = true;
     this._api.getCardElementManager().update();
   }