Update README, create CHANGELOG.md

Signed-off-by: dkwon17 <[email protected]>

CHANGELOG.md

@@ -0,0 +1,11 @@
+# CHANGELOG
+
+## v1.1.0
+- [Introduce webhook to prevent more than 1 KIP resource in a single namespace #115](https://github.com/che-incubator/kubernetes-image-puller-operator/pull/115)
+    - The Kubernetes Image Puller Operator now deploys a validating webhook to prevent more than one `KubernetesImagePuller` custom resource from being created in the same namespace.
+    - For Kubernetes clusters, [cert-manager](https://github.com/cert-manager/cert-manager) operator must be installed in order to serve the validating webhook.
+    - Names of resources that are created alongside the Kubernetes Image Puller Operator installation has been renamed.
+        - The `controller-manager-metrics-service` Service has been renamed to `kubernetes-image-puller-operator-manager-metrics-service`
+        - The `metrics-reader` ClusterRole has been renamed to `kubernetes-image-puller-operator-metrics-reader`
+        - The `kubernetes-image-puller-operator` ServiceAccount has been renamed to `kubernetes-image-puller-operator-sa`
+        - The ` kubernetes-image-puller-operator` Deployment has been renamed to `kubernetes-image-puller-operator-manager`

README.md

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 ### Installing The Operator
 
+> Notice: starting from version 1.1.0, this operator requires the cert-manager operator for serving validating webhooks on Kubernetes clusters. This is not required for installation on OpenShift clusters. To install cert-manager on a Kubernetes cluster run:
+```
+kubectl apply --validate=false -f https://github.com/cert-manager/cert-manager/releases/download/v1.13.3/cert-manager.yaml
+```
+
 #### Installing from OperatorHub
 
 > Notice: to install operator using OperatorHub you need to have Kubernetes cluster with pre-installed OLM.