added the liveReloadPort as an option for docker (#272)

content/notes/docker.md

@@ -26,6 +26,7 @@ services:
       - HUGO_BASEURL=http://localhost
       - HUGO_PORT=1313
       - HUGO_APPENDPORT=true
+      - HUGO_LIVERELOADPORT=-1
 ```
 
 Then run with: `docker-compose up -d` in the same directory as your `docker-compose.yml` file.