docs: add release notes for v1.4.0

Author: github-actions[bot]

release_notes/v1.4.0.md

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+# [1.4.0](https://github.com/NHSDigital/eps-devcontainers/compare/v1.3.0...v1.4.0) (2026-04-01)
+
+
+### New
+
+* [AEA-0000] - add anchore tools (#69) ([4325c48](https://github.com/NHSDigital/eps-devcontainers/commit/4325c4844f12f682edfd27ed7166c79ba143f4e8))
+
+## Info
+[Release workflow run](https://github.com/NHSDigital/eps-devcontainers/actions/runs/23845523548) - Workflow ID: 23845523548
+
+It was initialized by [anthony-nhs](https://github.com/anthony-nhs)
+
+