title: Gulp error - "ReferenceError: series is not defined"
body: <p>I'm getting this Reference error on this line: </p>
  
  <pre><code>gulp.watch(paths.src.html, series(copyHtml, browserSyncReload));
  </code></pre>
  
  <p>I can't figure out how to fix the problem.  Any suggestions?</p>
  
  <p><strong>gulpfile.js</strong></p>
  
  <pre><code>// BrowserSync
  function browserSync(done) {
      browsersync.init({
          open: false,
          server: {
              baseDir: paths.dist.base
          },
      });
      done();
  }
  
  // BrowserSync Reload
  function browserSyncReload(done) {
      browsersync.reload();
      done();
  }
  
  // Watch files
  function watchFiles() {
      gulp.watch(paths.src.html, series(copyHtml, browserSyncReload));
      gulp.watch("./tailwind.js", css);
      gulp.watch(paths.src.js, series(minifyJs, browserSyncReload));
  }
  
  // Complex tasks
  const build = gulp.series(clean, css, minifyCss, minifyJs, purgeCSS);
  const watch = gulp.parallel(watchFiles, browserSync);
  
  exports.build = build;
  exports.default = watch;
  </code></pre>