add v2 beta note to readme

README.md

@@ -1,5 +1,7 @@
 # Gatsby + Netlify CMS Starter
 
+**Note:** This starter uses the [Gatsby v2 Beta](https://www.gatsbyjs.org/blog/2018-06-16-announcing-gatsby-v2-beta-launch/).
+
 This repo contains an example business website that is built with [Gatsby](https://www.gatsbyjs.org/), and [Netlify CMS](https://www.netlifycms.org): **[Demo Link](https://gatsby-netlify-cms.netlify.com/)**.
 
 It follows the [JAMstack architecture](https://jamstack.org) by using Git as a single source of truth, and [Netlify](https://www.netlify.com) for continuous deployment, and CDN distribution.