Add Tour of Beam Page (apache#27244)

* add tour of beam page to redirect.

* add tour of beam page to redirect.

* add tour of beam page to redirect.

website/www/site/content/en/get-started/tour-of-beam.md

@@ -0,0 +1,21 @@
+---
+title: "The Tour of Beam"
+---
+
+<!--
+Licensed 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.
+-->
+
+# The Tour of Beam
+
+The "Tour of Beam" is an interactive way of learning to write Beam code with a sandbox, where you can write and run pipelines while walking through various concepts. Please [click here](https://tour.beam.apache.org/) to try it out.