docs: update README

Author: benox3

README.md

@@ -1,3 +1,23 @@
 # react-data-scroller
 
 React component for scrolling large amounts of data efficiently
+
+**This is currently a WIP and is not yet ready for production use. The API is
+not stable and is still evolving. Use at your own risk!**
+
+![Screen Capture](/docs/assets/data-scroller-capture.gif)
+
+## Why?
+react-data-scroller was originally designed as a drop in replacement for
+[react-virtualized](https://github.com/bvaughn/react-virtualized) but focused
+on preventing the constant mounting, unmounting and repainting of entire rows
+that occurs. The focus is rendering your data in the most efficient way
+which involves only rerendering (no unmounts/mounts and only minimal repainting)
+of the rows and shifting the data around.
+
+**Feature Checklist**
+- [x] Column Groups
+- [ ] Scroll handling from parent
+- [ ] Horizontal Virtualization
+- [ ] Freezing any columns (Not just left)
+- [ ] Nested Groups