Update README with new idea issue

Author: github-actions[bot]

README.md

@@ -10,4 +10,5 @@ to propose a project idea, file an issue with the prefix `idea:` in the issue ti
 |-------|-------------|
 | [idea: fancy landing page for rddc](https://github.com/nf-osi/2025-sage-hack-ideas/issues/3) | We could spend some time building a snazzy-looking landing page for the rare disease data commons... |
 | [idea: build and deploy agentic workflow for bringing old data portal annotations "up to spec"](https://github.com/nf-osi/2025-sage-hack-ideas/issues/6) | requirements: - automated review and change proposal - HITL review of proposals - automated... |
+| [idea: "Data Graveyard" Rescue System](https://github.com/nf-osi/2025-sage-hack-ideas/issues/7) | Create a detection and intervention system for identifying datasets that are at risk of becoming... |
 <!-- IDEAS_TABLE_END -->