Add Docker commands for Middleman

README.md

@@ -140,6 +140,41 @@ Beware that:
 [review apps]: https://docs.gitlab.com/ce/ci/review_apps/
+## Use Docker to render the website
+
+If you don't have a proper environment available to run Middleman, you can use
+Docker to provide one for you locally on your machine. In order to have this
+working correctly, you need to have at least Git and Docker installed, and an
+internet connection available.
+
+1. Clone the repository in a local folder
+   ```
+   git clone git@gitlab.com:gitlab-com/www-gitlab-com.git
+   ```
+   
+2. Create a Docker container
+   ```
+   docker create --name middleman -v "$PWD/www-gitlab-com":/site -w /site -p 4567:4567 \
+     -e LC_ALL=C.UTF-8 ruby /bin/bash -c 'bundle install && bundle exec middleman'
+   ```
+   
+3. Start the container
+   ```
+   docker start middleman
+   ```
+
+4. Connect to `http://localhost:4567/
+
+5. Change your original content as usual, and see the changes in the browser as soon as
+you save the new version of the file (otherwise, just restart the container)
+
+6. When you have finished, stop the container 
+   ```
+   docker stop middleman
+   ```
+
+> **Note**: Subsequent runs will just require `docker start middleman`.
+
 ## Conclusion (please leave this at the bottom of the doc)
 In case someone forgot the most important commands and is catting this file from the command line we end by listing them:
@@ -155,4 +190,4 @@ or to execute the last two commands just run:
 ```
 bin/run
-```
\ No newline at end of file
+```