chore: add final copyright headers

v1/lib/server/__tests__/__fixtures__/sidebar.js

@@ -1,3 +1,10 @@
+/**
+ * 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.
+ */
+
 module.exports = {
   docs: {
     'First Category': ['doc1', 'doc2'],

v1/lib/server/__tests__/__fixtures__/test.css

@@ -4,6 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  */
+
 .hljs {
   margin-left: -15px;
   margin-right: -15px;