message: build(docs-infra): update project structure to cli@9 5/12 (`polyfills.ts`)
  Update `polyfills.ts` (`import './zone-flags.ts'` --> `import './zone-flags'`).
  PR Close
diff: * will put import in the top of bundle, so user need to create a separate file
  * in this directory (for example: zone-flags.ts), and put the following flags
  * into that file, and then add the following code before importing zone.js.
  - * import './zone-flags.ts';
  + * import './zone-flags';
  *
  * The flags allowed in zone-flags.ts are listed here.
  *
  