Document how to add additional labels and annotations to skupper owned resources

[fgiorgetti]

Document how to pass additional labels and annotations to Skupper owned resources:

apiVersion: v1
kind: ConfigMap
metadata:
  name: skupper-labels
  labels:
    skupper.io/label-template: ""
    mylabel1: myvalue1
  annotations:
    myannotation1: myvalue1

It is also possible to filter which resources are going to be included, using .data setion, like:

data:
  kind: Deployment
  name: skupper-router

[pwright]

will be fixed by #292 ?