📖 add notice to make bring awarness to the need to move away and no longer use old images provide via the registry (kubernetes-sigs#4363)

add notice to make bring awarness to the need to move away and no longer use old images provide via the registry

Author: camilamacedo86

README.md

@@ -1,3 +1,11 @@
+> ⚠️ **IMPORTANT NOTICE:** Images under `gcr.io/kubebuilder/` Will Be Unavailable Soon
+>
+> 🚨The image `gcr.io/kubebuilder/kube-rbac-proxy,` will become unavailable.
+> Your projects will be affected and may fail to work if the image cannot be pulled.
+> You must move as soon as possible, sometime from early 2025, the GCR will go away.🚨
+>
+> For more information and guidance see the discussion https://github.com/kubernetes-sigs/kubebuilder/discussions/3907
+
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