message: Added comment for the mapper argument of the define:webserver emitHook declaration.
diff: @@ -114,6 +114,10 @@ export class Context extends events.EventEmitter {
  */
  emitHook(
  name: 'define:webserver', app: express.Express,
  + // The `mapper` param is a function the client of the hook uses to
  + // substitute a new app for the one given. This enables, for example,
  + // mounting the polyserve app on a custom app to handle requests or mount
  + // middleware that needs to sit in front of polyserve's own handlers.
  mapper: (app: Express.Application) => void, options: ServerOptions,
  done?: (err?: any) => void): Promise<void>;
  emitHook(
  