Added metadata to API content

Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/225225

doc/api/container_registry.md

+---
+stage: Package
+group: Package
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
 # Container Registry API
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/55978) in GitLab 11.8.

doc/api/deploy_keys.md

+---
+stage: Release
+group: Progressive Delivery
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
 # Deploy Keys API
 
 ## List all deploy keys

doc/api/deploy_tokens.md

+---
+stage: Release
+group: Progressive Delivery
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
 # Deploy Tokens API
 
 ## List all deploy tokens