remove trailing comma in package.json

package.json

@@ -5,7 +5,7 @@
     "main": "index.js",
     "scripts": {
         "build": "node_modules/.bin/rollup -c rollup.config.js",
-        "watch": "onchange '*.js' -v -- npm run build",
+        "watch": "onchange '*.js' -v -- npm run build"
     },
     "author": "S.Volke",
     "license": "MIT",