DOCS-2583 Add docs site front matter

[ruthnaebeck]

What does this PR do?

Add docs site front matter

Motivation

Front matter should live with the docs

Testing Guidelines

N/A

Additional Notes

https://github.com/DataDog/documentation/pull/12788

Types of changes

• [ ] Bug fix
• [ ] New feature
• [ ] Breaking change
• [ ] Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• [ ] This PR's description is comprehensive
• [ ] This PR contains breaking changes that are documented in the description
• [ ] This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• [ ] This PR impacts documentation, and it has been updated (or a ticket has been logged)
• [ ] This PR's changes are covered by the automated tests
• [ ] This PR collects user input/sensitive content into Datadog

[nhinsch]

How will this appear in the README within GitHub?

[ruthnaebeck]

How will this appear in the README within GitHub?

https://github.com/DataDog/datadog-cloudformation-macro/blob/40b2753df03fbd183a6e193fe5c49f3b2d293de4/serverless/README.md