refactor(cssnano-preset): migrate to TS (#7440)

* refactor(cssnano-preset): migrate to TS

* fix

packages/docusaurus-cssnano-preset/src/index.ts

@@ -0,0 +1,27 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import advancedBasePreset from 'cssnano-preset-advanced';
+import postCssSortMediaQueries from 'postcss-sort-media-queries';
+import postCssRemoveOverriddenCustomProperties from './remove-overridden-custom-properties';
+
+const preset: typeof advancedBasePreset = function preset(opts) {
+  const advancedPreset = advancedBasePreset({
+    autoprefixer: {add: false},
+    discardComments: {removeAll: true},
+    ...opts,
+  });
+
+  advancedPreset.plugins.unshift(
+    [postCssSortMediaQueries, undefined],
+    [postCssRemoveOverriddenCustomProperties, undefined],
+  );
+
+  return advancedPreset;
+};
+
+export = preset;