Setup Renovate for docker-compose

[pascalwilbrink]

Since Dependabot doesn't support Docker-Compose files, we need to have a different provider that supports Docker-Compose files.
Luckily, Renovate (OpenSource) does.

We can have Renovate next to the current Dependabot to only look into the Docker-Compose file and create a PR whenever a newer version of a docker image is released.

https://docs.renovatebot.com/modules/manager/docker-compose/

https://developer.mend.io/ is used; it is connected to the organisation;
Renovate will not create pull-request that are already made by dependabot;

Acceptance criteria:
Renovate will creat pull-requests when their is a new image in dockerhub for one of the services