Add git submodule update for running hugo locally

Author: makocchi-git

README.md

@@ -13,6 +13,7 @@ To run the website locally when you have Hugo installed:
 ```bash
 git clone https://github.com/kubernetes/website.git
 cd website
+git submodule update --init --recursive
 hugo server --buildFuture
 ```
 
@@ -62,4 +63,4 @@ Participation in the Kubernetes community is governed by the [CNCF Code of Condu
 
 ## Thank you!
 
-Kubernetes thrives on community participation, and we appreciate your contributions to our website and our documentation!
+Kubernetes thrives on community participation, and we appreciate your contributions to our website and our documentation!