Add README.md (i3#2910)

Author: CyberShadow

README.md

@@ -0,0 +1,12 @@
+![Logo](docs/logo-30.png) i3: A tiling window manager
+=====================================================
+
+[![Build Status](https://travis-ci.org/i3/i3.svg?branch=next)](https://travis-ci.org/i3/i3)
+[![Issue Stats](http://www.issuestats.com/github/i3/i3/badge/issue?style=flat)](http://www.issuestats.com/github/i3/i3)
+[![Pull Request Stats](http://www.issuestats.com/github/i3/i3/badge/pr?style=flat)](http://www.issuestats.com/github/i3/i3)
+
+i3 is a tiling window manager for X11.
+
+For more information about i3, please see [the project's website](https://i3wm.org/) and [online documentation](https://i3wm.org/docs/).
+
+For information about contributing to i3, please see [CONTRIBUTING.md](.github/CONTRIBUTING.md).