Examine source code of Catifier

{
  "name": "Catify",
  "version": "1.0",
  "manifest_version": 2,
  "content_security_policy": "default-src 'self'",
  "description": "Replaces all images on the internet with random cats",
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Replaces all images on the internet with random cats",
    "default_popup": "extension.html"
  },
  "applications": {
    "gecko": {
      "id": "addon@jossafossa.nl",
      "strict_min_version": "58.0"
    }
  },
  "permissions": [
    "http://fonts.googleapis.com/",
    "https://fonts.googleapis.com/",
    "tabs",
    "http://*/*",
    "https://*/*",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "main.css"
      ],
      "js": [
        "settingsWatcher.js",
        "main.js"
      ]
    }
  ],
  "icons": {
    "512": "icon.png"
  }
}