title: How can I add CSS file in the middle of Gulp.js task?
body: <p>How can I add CSS file in the middle of a pipe?</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>gulp.task('css', function () {
    var processors = [
      // list of PostCSS plugins
    ];
    return gulp.src('src/css/style.css') // Add style.css
      .pipe(postcss(processors)) // Use PostCSS
      .pipe(uncss({
          html: ['dist/index.html'] // Remove unused selectors
      }))
    // And here I want to add some other CSS file
      .pipe(nano()) // Minify CSS
      .pipe(gulp.dest('dist/css/'));
  });</code></pre>
  </div>
  </div>
  </p>
  
  <p>Gulp-add-src not works with CSS files.
  .pipe(gulp.src('src/css/other.css')) -> also not works</p>
  
  <p>How can I solve this problem?</p>