chore(demo-app): fix aligned menu triggers and add make page scrollable (#8280)

Author: willshowell

src/demo-app/menu/menu-demo.html

@@ -167,3 +167,5 @@
     </mat-menu>
   </div>
 </div>
+
+<div style="height: 500px">This div is for testing scrolled menus.</div>

src/demo-app/menu/menu-demo.scss

@@ -8,6 +8,6 @@
   }
 
   .end-icon {
-    align-items: flex-end;
+    justify-content: flex-end;
   }
 }