Use tfstate-lookup with GCS buckets backend

[dex4er]

Thi new version of tfstate-lookup supports GCS bucket so this is possible to run something like:

echo 'name: ref+tfstate:////home/piotr.roszatycki/Terraform/test/.terraform/terraform.tfstate/module.cluster-test.helm_release.velero.name' | vals eval -f -
name: velero

where terraform.tfstate file contains something like:

{
    "version": 3,
    "serial": 1,
    "lineage": "a0b37c38-a66d-11eb-8386-00155d223a60",
    "backend": {
        "type": "gcs",
        "config": {
            "access_token": null,
            "bucket": "test-terraform-state",
            "credentials": null,
            "encryption_key": null,
            "impersonate_service_account": null,
            "impersonate_service_account_delegates": null,
            "path": null,
            "prefix": null,
            "project": null,
            "region": null
        },
        "hash": 2718492160
    },
    "modules": [
        {
            "path": [
                "root"
            ],
            "outputs": {},
            "resources": {},
            "depends_on": []
        }
    ]
}

It should solve #38

[mumoshu]

LGTM. Thanks a lot for your contribution @dex4er ☺️