Merge branch 'koding-docker-compose-init' into 'master'

Add docker-compose environment initialization command

## What does this MR do?

Updates a snippet for setting up koding docker-compose environment in the integration document.

See merge request !7091

doc/administration/integration/koding.md

@@ -61,6 +61,7 @@ executing commands in the following snippet.
 ```bash
 git clone https://github.com/koding/koding.git
 cd koding
+docker-compose -f docker-compose-init.yml run init
 docker-compose up
 ```