0.12.0 [nginx-default-backend] Add `selector` to `Deployment`

what

• [nginx-default-backend] Add selector to Deployment

why

• Newer Kubernetes versions require selector to be present in DeploymentSpec
• Otherwise, the following error is thrown:

failed processing release ingress-backend: helm exited with status 1:
  Error: unable to build kubernetes objects from release manifest: error validating "": error validating data: ValidationError(Deployment.spec): missing required field "selector" in io.k8s.api.apps.v1.DeploymentSpec

references

• https://stackoverflow.com/questions/59369174/unable-to-helm-install-due-to-deployment-manifest-issue