⚠️ Inform users about the deprecation of the PR title validation GitH…

…ub Action

This commit informs users that the GitHub Action used for PR title validation is deprecated due to the upcoming unavailability of the images hosted under `gcr.io/kubebuilder/`, effective March 18, 2025.

Users are guided to replicate the functionality by creating a custom GitHub Action, following the approach used in the Kubebuilder project:
- A GitHub Action to trigger the validation: https://github.com/kubernetes-sigs/kubebuilder/blob/master/.github/workflows/verify.yml
- A shell script for checks: https://github.com/kubernetes-sigs/kubebuilder/blob/master/test/pr-title-checker.sh

README.md

@@ -16,7 +16,14 @@ $ go run sigs.k8s.io/kubebuilder-release-tools/notes
 $ go run sigs.k8s.io/kubebuilder-release-tools/notes -r beta
 ```
 
-## PR Verification GitHub Action
+## PR Verification GitHub Action (Deprecated)
+
+**IMPORTANT**: Images provided under `gcr.io/kubebuilder/` will be unavailable starting **March 18, 2025**. Therefore, this GitHub Action as described below will no longer work once the images are unavailable.
+
+> The functionality of this deprecated GitHub Action can be replicated using the current approach in the Kubebuilder project. Here’s how:
+> - Create a GitHub Action to trigger the validation, as demonstrated in the [Kubebuilder repository](https://github.com/kubernetes-sigs/kubebuilder/blob/master/.github/workflows/verify.yml).
+> - Ensure that the GitHub Action calls the necessary shell script for checks. You can find an example here: [pr-title-checker.sh](https://github.com/kubernetes-sigs/kubebuilder/blob/master/test/pr-title-checker.sh).
+
 
 This repository acts as a GitHub action for verifying PR titles match the
 [release notes generation requirements](/VERSIONING.md), as well as some