Examine source code of Sparkles <3

{
  "manifest_version": 2,
  "name": "Sparkles",
  "version": "1.3",
  "description": "Sparkles at you fingertips.",
  "icons": {
    "48": "icons/sparkly-48.png",
    "64": "icons/sparkly-64.png",
    "96": "icons/sparkly-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "sparkly.js"
      ]
    }
  ]
}