Add kustomize as development prerequisite (#27)

diff --git a/docs/development.md b/docs/development.md
index b4288f6..b1a5e85 100644
--- a/docs/development.md
+++ b/docs/development.md
@@ -27,7 +27,7 @@
 $ git clone git@github.com:apache/airflow-on-k8s-operator.git
 ```
 
-## Install kubebuilder
+## Install prerequisites
 You have to install the [kubebuilder](https://book.kubebuilder.io/quick-start.html):
 ```shell script
 os=$(go env GOOS)
@@ -42,6 +42,12 @@
 export PATH=$PATH:/usr/local/kubebuilder/bin
 ```
 
+Also the [kustomize](https://github.com/kubernetes-sigs/kustomize) is required. On MacOS:
+```shell script
+brew install kustomize
+```
+For other installation options check https://github.com/kubernetes-sigs/kustomize/blob/master/docs/INSTALL.md
+
 
 ## Building and running locally:
 ```bash