[docs] Fix the link of 'edit on github' on site (#578)

docs/_templates/breadcrumbs.html

@@ -0,0 +1,52 @@
+<!--
+  ~ Licensed to the Apache Software Foundation (ASF) under one
+  ~ or more contributor license agreements.  See the NOTICE file
+  ~ distributed with this work for additional information
+  ~ regarding copyright ownership.  The ASF 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.
+-->
+
+<!-- Extend the RTD template to support user defined "Edit on Github" URL -->
+{%- extends "sphinx_rtd_theme/breadcrumbs.html" %}
+
+{% if page_source_suffix %}
+    {% set suffix = page_source_suffix %}
+{% else %}
+    {% set suffix = source_suffix %}
+{% endif %}
+
+{% if meta is defined and meta is not none %}
+    {% set check_meta = True %}
+{% else %}
+    {% set check_meta = False %}
+{% endif %}
+
+{% if check_meta and 'github_url' in meta %}
+    {% set display_github = True %}
+{% endif %}
+
+
+<div role="navigation" aria-label="breadcrumbs navigation">
+    <ul class="wy-breadcrumbs">
+        {% block breadcrumbs_aside %}
+            <li class="wy-breadcrumbs-aside">
+                {% if pagename != "search" %}
+                    {% if display_github %}
+                        <a href="http://{{ github_host|default("github.com") }}/{{ github_user }}/{{ github_repo }}/blob/{{ github_version }}/docs/{{ pagename }}{{ suffix }}" class="fa fa-github"> {{ _('Edit on GitHub') }}</a>
+                    {% endif %}
+                {% endif %}
+            </li>
+        {% endblock %}
+    </ul>
+    <hr/>
+</div>