SPEG - README.md updated

Author: obenjiro

README.md

@@ -3,3 +3,12 @@
 [![Coverage Status](https://coveralls.io/repos/github/SimplePEG/JavaScript/badge.svg?branch=master)](https://coveralls.io/github/SimplePEG/JavaScript?branch=master)
 
 JavaScript version ( Browser and Node.js ) of SimplePEG
+
+```
+import {SPEG} from 'simplepeg';
+const parser = new SPEG();
+
+parser.parse_grammar('GRAMMAR test a->"A";);
+const ast = parser.parse_text('A');
+console.log(ast);
+```