feat: spinner while loading signin method

Signed-off-by: peterpeterparker <[email protected]>

Author: peterpeterparker

studio/src/app/components/core/app-signin/app-signin.scss

@@ -24,4 +24,10 @@ app-signin {
   strong {
     text-decoration: underline;
   }
+
+  div.spinner {
+    display: flex;
+    justify-content: center;
+    padding: 16px;
+  }
 }

studio/src/app/components/core/app-signin/app-signin.tsx

@@ -142,7 +142,11 @@ export class AppSignIn {
 
         {this.renderGitHub()}
 
-        {this.signIn}
+        {this.signIn || (
+          <div class="spinner">
+            <ion-spinner color="medium"></ion-spinner>
+          </div>
+        )}
       </Fragment>
     );
   }