add readme for the crd-puller

On-behalf-of: @SAP [email protected]

Author: xrstf

cmd/crd-puller/README.md

@@ -0,0 +1,17 @@
+# CRD Puller
+
+The `crd-puller` can be used for testing and development in order to export a
+CustomResourceDefinition for any Group/Version/Kind (GVK) in a Kubernetes cluster.
+
+The main difference between this and kcp's own `crd-puller` is that this one
+works based on GVKs and not resources (i.e. on `apps/v1 Deployment` instead of
+`apps.deployments`). This is more useful since a PublishedResource publishes a
+specific Kind and version.
+
+## Usage
+
+```shell
+export KUBECONFIG=/path/to/kubeconfig
+
+./crd-puller Deployment.v1.apps.k8s.io
+```