add lightweight umami image

recently we disentangled the package dependencies for plotting etc. to not depend anymore on tensorflow.

We could now build a light docker image which can be used for plotting not including tensorflow/keras

added CI/CD label

mentioned in merge request !473 (merged)

mentioned in merge request !482 (merged)

closed with commit fca80dd3

closed with merge request !482 (merged)

mentioned in commit fca80dd3