update README

Author: mackierx111

README.md

@@ -12,7 +12,7 @@ AWSIM is the best scene simulator for [Autoware](https://github.com/autowarefoun
 - Open source software
 - Made with Unity Game Engine
 
-First, try the tutorial. [AWSIM Document - Quick Start Demo](XXX)
+First, try the tutorial. [AWSIM Document - Quick Start Demo](https://tier4.github.io/AWSIM/GettingStarted/QuickStartDemo/)
 
 ## License