Examine source code of Font Changer

{
  "manifest_version": 2,
  "name": "Font Changer",
  "version": "2.0",
  "description": "Change the page font instantly with a simple click from a list of over 800 different fonts. Save preferences per site, preview fonts, and customize typography.",
  "icons": {
    "32": "icons/font-32.png",
    "48": "icons/font-48.png",
    "96": "icons/font-96.png"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_scripts/fontChange.js"
      ],
      "run_at": "document_end"
    }
  ],
  "applications": {
    "gecko": {
      "id": "fontchanger@hareblounes.com"
    }
  },
  "browser_action": {
    "default_icon": "icons/font-32.png",
    "default_title": "Font Changer",
    "default_popup": "popup/font_changer.html"
  }
}