Update grunt-contrib-jshint to the latest version 🚀 (#20)

## The devDependency [grunt-contrib-jshint](https://github.com/gruntjs/grunt-contrib-jshint) was updated from `1.1.0` to `2.0.0`.
This version is **not covered** by your **current version range**.

If you don’t accept this pull request, your project will work just like it did before. However, you might be missing out on a bunch of new features, fixes and/or performance improvements from the dependency update.

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[Find out more about this release](https://github.com/gruntjs/grunt-contrib-jshint).

<details>
  <summary>FAQ and help</summary>

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package.json

@@ -21,7 +21,7 @@
     "grunt-contrib-concat": "~1.0.1",
     "grunt-contrib-connect": "~2.0.0",
     "grunt-contrib-copy": "~1.0.0",
-    "grunt-contrib-jshint": "~1.1.0",
+    "grunt-contrib-jshint": "~2.0.0",
     "grunt-contrib-uglify": "~3.4.0",
     "grunt-contrib-watch": "~1.0.0",
     "grunt-html": "~9.3.0",