Examine source code of Font Changer

{
  "manifest_version": 2,
  "name": "Font Changer",
  "version": "1.0",
  "description": "Extension to change fonts on webpages",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "images/icon-16.png",
      "48": "images/icon-48.png",
      "128": "images/icon-128.png"
    }
  },
  "icons": {
    "48": "images/icon-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ab21fcac-2c7e-404b-aeee-c6e8febb6d05}"
    }
  }
}