build: fix dev-app deployment to firebase (#14529)

firebase.json

@@ -1,6 +1,6 @@
 {
   "hosting": {
-    "public": "dist/packages/dev-app",
+    "public": "dist/devapp-deploy",
     "rewrites": [
       {
         "source": "/**/!(*.@(js|ts|html|css|json|svg|png|jpg|jpeg))",

tools/gulp/tasks/development.ts

@@ -85,6 +85,7 @@ task('serve:devapp', ['build:devapp'], sequenceTask([':serve:devapp', ':watch:de
 task('stage-deploy:devapp', ['build:devapp'], () => {
   const deployOutputDir = join(outputDir, 'devapp-deploy');
 
+  copyFiles(outDir, 'index.html', deployOutputDir);
   copyFiles(outDir, '**/*.+(css|js|map)', deployOutputDir);
   copyFiles(join(projectDir, 'node_modules'), vendorGlob, join(deployOutputDir, 'node_modules'));
   copyFiles(bundlesDir, '*.+(js|map)', join(deployOutputDir, 'dist/bundles'));