Add require() to first usage example

README.md

@@ -21,6 +21,8 @@ npm install build-output-script
 Send 1 BTC to `1LukeQU5jwebXbMLDVydeH4vFSobRV9rkj`
 
 ```js
+const buildOutputScript = require('build-output-script');
+
 buildOutputScript([{address: '1LukeQU5jwebXbMLDVydeH4vFSobRV9rkj', value: 100000000}]);
 // '0100e1f505000000001976a914da6473ed373e08f46dd8003fca7ba72fbe9c555e88ac'
 ```