fix: add default ROLLOUT_RESOURCE_TYPE=deployment
Needing to specify ROLLOUT_RESOURCE_TYPE is an obscure implementation
detail that most user should not need to care about. We don't even have
built-in support for other types, so we should not force users to set
it.
This is especially relevant to users who include
Jobs/Deploy.gitlab-ci.yml instead of Auto-DevOps.gitlab-ci.yml.
Edited by Hordur Freyr Yngvason