fix(bootstrap): return promise and resolve ionicBootstrap

Closes #7145

Author: adamdbradley

src/components/nav/test/basic/index.ts

@@ -417,4 +417,6 @@ class E2EApp {
   }
 }
 
-ionicBootstrap(E2EApp);
+ionicBootstrap(E2EApp).then((componetRef) => {
+  console.log('ionicBootstrap', componetRef);
+});

src/config/bootstrap.ts

@@ -35,11 +35,14 @@ export function ionicBootstrap(appRootComponent: any, customProviders?: Array<an
   let providers = ionicProviders(customProviders, config);
   providers.push({provide: UserComponent, useValue: appRootComponent});
 
-  cssReady(() => {
-    // call angular bootstrap
-    bootstrap(AppRoot, providers).then(ngComponentRef => {
-      // ionic app has finished bootstrapping
-      ionicPostBootstrap(ngComponentRef);
+  return new Promise((resolve) => {
+    cssReady(() => {
+      // call angular bootstrap
+      bootstrap(AppRoot, providers).then(ngComponentRef => {
+        // ionic app has finished bootstrapping
+        ionicPostBootstrap(ngComponentRef);
+        resolve(ngComponentRef);
+      });
     });
   });
 }