docs: facelift the docs (#20180)

* docs: facelift the docs

* lint

* license headers

docs/src/styles/antd-theme.less

@@ -0,0 +1,27 @@
+/**
+ * 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.
+ */
+@primary-color: #20a7c9;
+@info-color: #66bcfe;
+@success-color: #59c189;
+@processing-color: #66bcfe;
+@error-color: #e04355;
+@highlight-color: #e04355;
+@normal-color: #d9d9d9;
+@white: #FFF;
+@black: #000;