feat: add envFrom ConfigMap to chart

[luanaBanana]

This adds the support to add envFrom with configMapRef through Helm Values:

I wasn't able to use an array of maps with the current setup, like this:

  chaoskube:
    env:
      - name: MY_VAR
        valueFrom:
          configMapKeyRef:
            name: chaoskube-cm1
            key: my-var

Results in: error converting YAML to JSON: yaml: line 39: did not find expected key

With this PR it will be possible to add the following:

  chaoskube:
    envFromConfigMapRefs:
       - chaoskube-cm1
       - chaoskube-cm2

What do you think, could this be merged?

[linki]

@luanaBanana Thanks!