Added EthereumClassic to the list of sites. (#427)

Added EthereumClassic to the list of created websites with Gatsby.

README.md

@@ -41,6 +41,7 @@ it'll be converted to `/docs/index.html`.
 * Live editing on every part of your site. Dramatically speed development.
 
 ## Sites built with Gatsby
+* [ethereumclassic.org](http://ethereumclassic.org/) ([source](https://github.com/ethereumclassic/ethereumclassic.github.io/tree/source))
 * [bricolage.io](https://bricolage.io/?utm_source=github.com) ([source](https://github.com/KyleAMathews/blog))
 * [relaterocket.co](https://relaterocket.co?utm_source=github.com)
 * [reindex.io](https://www.reindex.io)