dhi: add blog to resources (#24385)

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## Description

Added latest blog about DHI system packages announcement.


https://deploy-preview-24385--docsdocker.netlify.app/dhi/resources/#blog-posts

## Related issues or tickets

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## Reviews

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- [ ] Editorial review

Signed-off-by: Craig Osterhout <craig.osterhout@docker.com>

Author: craig-osterhout

content/manuals/dhi/resources.md

@@ -19,6 +19,7 @@ features, and announcements:
 
 | Date published | Title |
 |------|-------|
+| March 3, 2026 | [Announcing Docker Hardened System Packages](https://www.docker.com/blog/announcing-docker-hardened-system-packages/) |
 | January 25, 2026 | [Making the Most of Your Docker Hardened Images Enterprise Trial - Part 3](https://www.docker.com/blog/making-the-most-of-your-docker-hardened-images-enterprise-trial-part-3/) |
 | January 24, 2026 | [Making the Most of Your Docker Hardened Images Enterprise Trial - Part 2](https://www.docker.com/blog/making-the-most-of-your-docker-hardened-images-enterprise-trial-part-2/) |
 | December 19, 2025 | [Docker Hardened Images: Security Independently Validated by SRLabs](https://www.docker.com/blog/docker-hardened-images-security-independently-validated-by-srlabs/) |