docs: add release notes for v5.4.0

Author: github-actions[bot]

release_notes/v5.4.0.md

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+# [5.4.0](https://github.com/NHSDigital/eps-common-workflows/compare/v5.3.12...v5.4.0) (2026-02-12)
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+
+### New
+
+* [AEA-6028] - Updated actionlint to allow for yaml anchors (#63) ([ae3d6b3](https://github.com/NHSDigital/eps-common-workflows/commit/ae3d6b307b3174b5724a31f63776ce4159639d20))
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+
+
+
+## Info
+[Release workflow run](https://github.com/NHSDigital/eps-common-workflows/actions/runs/21942413870) - Workflow ID: 21942413870
+
+It was initialized by [anthony-nhs](https://github.com/anthony-nhs)
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+