feat: init deploy-gke Container Action (#5)

This commit inits the deploy-gke container action. It utlizes the
gke-deploy CLI image to deploy an existing image to a GKE cluster.

The integration test, documentation and CI setup are included within
this initial commit.

<!--
Thank you for proposing a pull request! Please note that SOME TESTS WILL
LIKELY FAIL due to how GitHub exposes secrets in Pull Requests from
forks.
Someone from the team will review your Pull Request and respond.

Please describe your change and any implementation details below.
-->

.github/workflows/integration.yml

@@ -56,7 +56,6 @@ jobs:
         cluster_name: '${{ vars.CLUSTER_NAME }}'
         project_id: '${{ vars.PROJECT_ID }}'
         namespace: '${{ vars.NAMESPACE }}'
-        expose: '${{ vars.EXPOSE }}'
 
     - name: 'get credentials'
       uses: 'google-github-actions/get-gke-credentials@v2'