message: Replace require() with dynamic import()
diff: import * as logging from 'plylog';
  import {ProjectConfig} from 'polymer-project-config';
  -import * as polyserveTypeOnly from 'polyserve';
  import {args as polyserveArgs} from 'polyserve/lib/args';
  import {ServerOptions} from 'polyserve/lib/start_server';
  -import * as urlTypeOnly from 'url';
  import {Environment} from '../environment/environment';
  @@ -40,10 +38,10 @@ export class ServeCommand implements Command {
  async run(options: CommandOptions, config: ProjectConfig) {
  // Defer dependency loading until this specific command is run
  - const polyserve = require('polyserve') as typeof polyserveTypeOnly;
  + const polyserve = await import('polyserve');
  const startServers = polyserve.startServers;
  const getServerUrls = polyserve.getServerUrls;
  - const url = require('url') as typeof urlTypeOnly;
  + const url = await import('url');
  let openPath: string|undefined;
  if (config.entrypoint && config.shell) {
  