code: function IndexHandler(req, res, next, local = false) {
              const parsedUrl = url.parse(req.url);
              if (!parsedUrl.pathname.startsWith(self.localFilesystemUrl) &&
                  parsedUrl.pathname !== '/favicon.ico'
              ) {
                  /** @type {Asset} */
                  const indexFile = self.assetBundle.getIndexFile();
                  if (local) {
                      createStreamProtocolResponse(indexFile.getFile(), res, () => {
                      });
                  } else {
                      send(req, encodeURIComponent(indexFile.getFile())).pipe(res);
                  }
              } else {
                  next();
              }
          }
docs: Serves index.html as the last resort.
  
  @param {Object} req        - request object
  @param {Object} res        - response object
  @param {Function} next     - called on handler miss
  @param {boolean} local - local mode