documentation: match frontmatter on docs site .md files

[jcstein]

Overview

This PR matches the frontmatter (metadata) config on the Celestia docs site. This is being added to the source on the orchestrator-relayer repository as it will prevent the frontmatter from being removed when imported from this repository.

You can see in this commit (ignore edit to package.json), a demonstration of what it would look like if the importMarkdown.mjs ran when the frontmatter does not exist on this source repository. This resolves #463

Checklist

• New and updated code has appropriate documentation
• New and updated code has new and/or updated testing
• Required CI checks are passing
• Visual proof for any user facing features like CLI or documentation updates
• Linked issues closed with keywords