feat(v2): render Markdown on server-side instead (#1077)

* feat(v2): render Markdown on server-side instead

* move to folder

v2/lib/webpack/loaders/markdown/anchors.js

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+const toSlug = require('./toSlug');
+
+function anchors(md) {
+  const originalRender = md.renderer.rules.heading_close;
+
+  // eslint-disable-next-line
+  md.renderer.rules.heading_close = function(tokens, idx, options, env) {
+    const textToken = tokens[idx - 1];
+
+    if (textToken.content) {
+      const anchor = toSlug(textToken.content, env);
+
+      return ` <a aria-hidden="true" id="${anchor}"></a><a aria-hidden="true" class="hash-link" href="#${anchor}">#</a></h${
+        tokens[idx].hLevel
+      }>
+`;
+    }
+
+    return originalRender(tokens, idx, options, env);
+  };
+}
+
+module.exports = anchors;