Allow creation of google_service_account_key

[kevcube]

We are creating a module which creates a new service account and stores its key in a secret store.

I am able to do..

module "service_account" {
  source = "mineiros-io/service-account/google"
}

resource "google_service_account_key" "key" {
  service_account = module.service_account.service_account
}

But it would be nice if we had the option to create a key in this module and view it as an output.

[nitesh8860]

I've added a PR accomplishing this request
https://github.com/mineiros-io/terraform-google-service-account/pull/38