docs(README.md): Add badge and link to ReadTheDocs

I did not know that this was where the docs were. This should solve that.

README.md

@@ -2,6 +2,7 @@
 
 [![Join the chat at https://gitter.im/ethereum/remix](https://badges.gitter.im/ethereum/remix.svg)](https://gitter.im/ethereum/remix?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 [![CircleCI](https://circleci.com/gh/ethereum/remix.svg?style=svg)](https://circleci.com/gh/ethereum/remix)
+[![Documentation Status](https://readthedocs.org/projects/docs/badge/?version=latest)](https://remix.readthedocs.io/en/latest/)
 
 Ethereum tools for the web.
 
@@ -18,6 +19,8 @@ Ethereum tools for the web.
 
 The **Remix IDE** is an IDE for Solidity dApp developers, powered by Remix. The Remix IDE repository **is available [here](https://github.com/ethereum/remix-ide)**, and an online version is available at https://remix.ethereum.org.
 
+For more, check out the [Remix documentation on ReadTheDocs](https://remix.readthedocs.io/en/latest/).
+
 ## <a name="how-to-use"></a>How to use Remix
 
 ### Prerequisites