Merge pull request #3874 from camilamacedo86/notefaq

📖 Add note to link Controller-Runtime FAQ page

docs/book/src/faq.md

@@ -1,6 +1,15 @@
 
 # FAQ
 
+<aside class="note">
+<h1> Controller-Runtime FAQ </h1>
+
+Kubebuilder is developed on top of the [controller-runtime](https://github.com/kubernetes-sigs/controller-runtime)
+and [controller-tools](https://github.com/kubernetes-sigs/controller-tools) libraries. We recommend you also check
+the [Controller-Runtime FAQ page](https://github.com/kubernetes-sigs/kubebuilder/issues/3873).
+</aside>
+
+
 ## How does the value informed via the domain flag (i.e. `kubebuilder init --domain example.com`) when we init a project?
 
 After creating a project, usually you will want to extend the Kubernetes APIs and define new APIs which will be owned by your project. Therefore, the domain value is tracked in the [PROJECT][project-file-def] file which defines the config of your project and will be used as a domain to create the endpoints of your API(s). Please, ensure that you understand the [Groups and Versions and Kinds, oh my!][gvk].