Overwrite kube config if set as env var

[grssmnn]

I had a problem running the kubectl action when using multiple environments running on their own cluster. Once set the kube config didn't change anymore even though I set a new one through KUBE_CONFIG.
Therefore, always overwrite the kube config if a new one is set through env vars.

[laszlof]

@grssmnn Ran into this same problem. Did you ever resolve this outside of this unmerged PR?

[grssmnn]

Hi @laszlof
you can add the adapted action to your repo and reference it by path in your workflow:

    steps:
      - uses: ./.github/actions/kubectl