phase-9: add builder sandbox for in-memory configuration editing

src/app/app.routes.ts

@@ -31,6 +31,10 @@ const coreRoutes: Routes = [
   {
     path: 'platform',
     loadComponent: () => import('./pages/public/platform-home.component').then(m => m.PlatformHomeComponent)
+  },
+  {
+    path: 'builder-sandbox',
+    loadComponent: () => import('./pages/builder/builder-sandbox.component').then(m => m.BuilderSandboxComponent)
   }
 ];