added yamllint to check all yaml files in the repo.
added yamllint to check all yaml files in the repo.

jens-maus/RaspberryMatic,jens-maus/RaspberryMatic,jens-maus/RaspberryMatic,jens-maus/RaspberryMatic,jens-maus/RaspberryMatic,jens-maus/RaspberryMatic