The deployment template creates jobs to deploy web apps to Cloud Run for the
development, staging and production environments.

Add additional comments to the deployment template about how to use it
(especially with regards to enironment variables). Highlight that the
deployment template doesn't create any jobs by default.

Split Terraform configuration file linting into a dedicated template.

Don't perform Terraform lint by default when using the deployment template
(as a deployment repository doesn't necessarily contain Terraform
configuration files).

Simplify the Terraform lint template (run `terraform` from the hashicorp
image).

Make `when: on_success` rule explicit in the Terraform lint template.

Add deployment template

Closes #6

See merge request !12