Update README.md (#65)

Just fixing a comma/semicolon typo.

Author: ebutleratlassian

README.md

@@ -66,7 +66,7 @@ pixelmatch image1.png image2.png output.png 0.1
 
 ```js
 const fs = require('fs');
-const PNG = require('pngjs').PNG,
+const PNG = require('pngjs').PNG;
 const pixelmatch = require('pixelmatch');
 
 const img1 = PNG.sync.read(fs.readFileSync('img1.png'));