Add Review workflow

[elithrar]

Adds the Review Bonk workflow.

• Invocations limited to CODEOWNERS
• Uses the "Docs" agent we have at https://github.com/cloudflare/cloudflare-docs/blob/production/.opencode/agent/docs.md
• Request a review by commenting:

/review

[github-actions]

This pull request requires reviews from CODEOWNERS as it changes files that match the following patterns:

Pattern	Owners
/.github/	@cloudflare/pcx-content-engineering, @cloudflare/content-engineering, @kodster28

[github-actions]

Preview URL: https://6ec90b95.preview.developers.cloudflare.com
Preview Branch URL: https://bonk-add-bonk-review.preview.developers.cloudflare.com

[elithrar]

App is now installed.

[elithrar]

needs an ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }} set