Remove old untagged container images

Author: mayuki

.github/workflows/build.yaml

@@ -44,4 +44,11 @@ jobs:
           platforms: linux/amd64
           push: true
           tags: ${{ steps.meta.outputs.tags }}
-          labels: ${{ steps.meta.outputs.labels }}
+          labels: ${{ steps.meta.outputs.labels }}
+      - uses: actions/delete-package-versions@e5bc658cc4c965c472efe991f8beea3981499c55 #v5.0.0
+        with:
+          package-name: ${{ env.IMAGE_NAME }}
+          package-type: 'container'
+          min-versions-to-keep: 5
+          delete-only-untagged-versions: true
+          token: ${{ secrets.GITHUB_TOKEN }}