docs: simple docs for conversion hooks (#38)

Author: csviri

README.md

@@ -1,11 +1,14 @@
 # admission-controller-framework
 
 Framework and tooling to support
-implementing [admission controllers](https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/) for
-Kubernetes in Java. Supports both **quarkus** and **spring boot**. Both Sync and Async programing model.
+implementing [admission controllers](https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/)
+and [conversion hooks](https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definition-versioning/#webhook-conversion)
+for Kubernetes in Java. Supports both **quarkus** and **spring boot**. Both Sync and Async programing model.
 
 ## Sample Usage
 
+### Admission Controllers
+
 Defining a mutation or validation controller is simple as:
 
 https://github.com/java-operator-sdk/admission-controller-framework/blob/0946595d941b789caef6a69b34c2e5be8c6b59cf/samples/quarkus/src/main/java/io/javaoperatorsdk/admissioncontroller/sample/quarkus/AdmissionControllerConfig.java#L31-L68
@@ -15,3 +18,19 @@ What can be then simple used in an endpoint:
 https://github.com/java-operator-sdk/admission-controller-framework/blob/0946595d941b789caef6a69b34c2e5be8c6b59cf/samples/quarkus/src/main/java/io/javaoperatorsdk/admissioncontroller/sample/quarkus/AdmissionEndpoint.java#L57-L89
 
 See samples also for details.
+
+### Conversion Hooks
+
+Conversion hooks follows the same patter described
+in [Kuberbuilder](https://book.kubebuilder.io/multiversion-tutorial/conversion-concepts.html), thus first converts the
+custom resource from actual version to a hub, and as next step from the hub to the target resource version.
+
+To create the controller
+register [mappers](https://github.com/java-operator-sdk/admission-controller-framework/blob/main/core/src/main/java/io/javaoperatorsdk/webhook/conversion/Mapper.java)
+:
+
+https://github.com/java-operator-sdk/admission-controller-framework/blob/2a2bce54b49ea3398bef95a9102ee8645e11cf87/samples/quarkus/src/main/java/io/javaoperatorsdk/webhook/admission/sample/quarkus/conversion/ConversionControllerConfig.java#L15-L29
+
+and use the controllers in the endpoint:
+
+https://github.com/java-operator-sdk/admission-controller-framework/blob/2a2bce54b49ea3398bef95a9102ee8645e11cf87/samples/spring-boot/src/main/java/io/javaoperatorsdk/webhook/sample/springboot/conversion/ConversionEndpoint.java#L29-L40