docs(style): make more responsive for mobile (#10853)

* docs(style): make more responsive for mobile

* Make a responsive navbar

* more fixes and tweaks

* Add README instructions

docs/src/components/AnchorNavigator.tsx

@@ -0,0 +1,62 @@
+/**
+ * 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.
+ */
+import React from 'react';
+import { Anchor } from 'antd';
+import { useMenus } from 'docz';
+import { css } from '@emotion/core';
+import { getActiveMenuItem, mq } from '../utils';
+
+const { Link } = Anchor;
+const anchorNavStyle = css`
+
+    ${[mq[3]]} {
+      display: none;
+    }
+    position: fixed;
+    top: 64px;
+    right: 0;
+    width: 250px;
+    padding: 16px;
+    height: 605px;
+    overflow: auto;
+    ul {
+      font-size: 12px;
+      li {
+        height: 25px;
+        line-height: 25px;
+        word-wrap: break-word;
+      }
+    }
+`;
+
+const HeaderNav = () => {
+  const menus = useMenus();
+  const { headings } = getActiveMenuItem(menus);
+  return (
+    <div css={anchorNavStyle}>
+      <Anchor>
+        {headings.map((e) => (
+          <Link href={`#${e.slug}`} title={e.value} />
+        ))}
+      </Anchor>
+    </div>
+  );
+};
+
+export default HeaderNav;