Add instructions for staging site using Docker (#9217)

* Add instructions for staging site using Docker

Adds a condensed version of the instructions in the README to
the intermediate contribution page.

* Format code blocks

content/en/docs/contribute/intermediate.md

@@ -504,6 +504,22 @@ changes look like, you can use the `hugo` command to stage the changes locally.
 4.  To stop the local Hugo instance, go back to the terminal and type `Ctrl+C`
     or just close the terminal window.
 
+Alternatively, you can build the Kubernetes docs using Docker.
+
+1.  Build the image locally:
+
+      ```bash
+      make docker-image
+      ```
+
+2.  Once the `kubernetes-hugo` image has been built locally, you can build and serve the site:
+
+      ```bash
+      make docker-serve
+      ```
+
+3.  In your browser's address bar, enter `localhost:1313`. Hugo will watch the
+filesystem for changes and rebuild the site as needed.
 
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