Add quick sort.

Author: trekhleb

README.md

@@ -75,6 +75,7 @@ npm test -- -t 'playground'
 Order of growth of algorithms specified in Big O notation.
 
 ![Big O graphs](https://github.com/trekhleb/javascript-algorithms/blob/master/assets/big-o-graph.png)
+
 Source: [Big O Cheat Sheet](http://bigocheatsheet.com/).
 
 Below is the list of some of the most used Big O notations and their performance comparisons against different sizes of the input data.