Build Cloudflare module documentation site

In gitlab-com/content-sites/handbook!13775 (merged) we have defined a centralized documentation site for the set of Terraform modules we are defining. This will enable engineers to self-serve for their implementation of the modules, and provides a centralized location to provide upgrade documentation and migration steps where required.

Proposal

• Automation to aggregate documentation from the specialized modules
• Build the pages site using local and aggregated documentation
• Configure a pages site on the entrypoint repository
  • This should be visible to GitLab team members only as some documentation may be unsuitable for general distribution