add link to preview build

Author: alexkrolick

README.md

@@ -3,4 +3,6 @@ react-testing-library-docs
 
 Documentation site for [react-testing-library](https://github.com/kentcdods/react-testing-library)
 
-See [./website/README.md](./website/README.md) for instructions on building the site
+See [./website/README.md](./website/README.md) for instructions on building the site
+
+**Deployed on Netlify: https://react-testing-library-docs.netlify.com/**