Examine source code of Self Butler

{
  "name": "Self Butler",
  "description": "Shortcuts to Self Butler",
  "icons": {
    "48": "icon.png",
    "128": "icon128.png"
  },
  "version": "1.0.22",
  "permissions": [
    "tabs",
    "topSites",
    "storage",
    "*://*.selfbutler.com/*"
  ],
  "browser_action": {
    "default_title": "Self Butler",
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "chrome_url_overrides": {
    "newtab": "newtab/index.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.selfbutler.com/*"
      ],
      "js": [
        "injectTopSites.js"
      ],
      "css": [
        "topsites.css"
      ]
    },
    {
      "matches": [
        "*://*.selfbutler.com/*"
      ],
      "js": [
        "noextwarning.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "style.css",
    "*.png"
  ],
  "default_locale": "en",
  "manifest_version": 2,
  "applications": {
    "gecko": {
      "id": "{29828a3b-b422-4c85-a683-1f738fba9d16}",
      "strict_min_version": "57.0"
    }
  }
}