Examine source code of Print Preview Clean

{
  "manifest_version": 2,
  "name": "Print Preview Clean",
  "version": "1.1",
  "description": "Cleans the page for better printing by removing headers, sidebars, ads and footers.",
  "icons": {
    "64": "icons/icon64.png",
    "128": "icons/icon128.png"
  },
  "browser_action": {
    "default_title": "Clean & Print",
    "default_icon": "icons/icon64.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{65ac99d0-a424-4077-bd97-fd6b0a2c3e75}",
      "strict_min_version": "114.0"
    }
  }
}