feat: Add placeholder landing pages for NAP

[ADubhlaoich]

Proposed changes

This commit adds placeholder landing pages for NGINX App Protect WAF & DoS: there is much more coherent landing page as part of the formal refactor. These changes exist to unblock Mainframe, a new theme design, from releasing. It also addresses a call-out regression.

Checklist

Before sharing this pull request, I completed the following checklist:

• I read the Contributing guidelines
• My branch adheres to the Git conventions
• My content changes adhere to the F5 NGINX Documentation style guide
• If my changes involve potentially sensitive information¹, I have assessed the possible impact
• I have waited to ensure my changes pass tests, and addressed any discovered issues

Footnotes

1. Potentially sensitive information includes personally identify information (PII), authentication credentials, and live URLs. Refer to the style guide for guidance about placeholder content. ↩

[github-actions]

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[mjang]

Suggested changes for consistency with other landing pages (icon, importance of RN)