restore dummy documentation_links.ts file to fix doc build

src/legacy/ui/public/documentation_links/documentation_links.ts

@@ -0,0 +1,28 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/*
+  WARNING: The links in this file are validated during the docs build. This is accomplished with some regex magic that
+  looks for these particular constants. As a result, we should not add new constants or change the existing ones.
+  If you absolutely must make a change, talk to Clinton Gormley first so he can update his Perl scripts.
+ */
+export const DOC_LINK_VERSION = 'stub';
+export const ELASTIC_WEBSITE_URL = 'stub';
+
+export const documentationLinks = {};