Examine source code of Page Fold Marker

{
  "manifest_version": 2,
  "name": "Page Fold Marker",
  "version": "1.0",
  "description": "Displays fold markers on pages for printing guidance",
  "icons": {
    "48": "icons/page-fold-marker.ico"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Page Fold Marker"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "folds.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{cf6782c3-7162-478c-b459-2b51501e7d15}"
    }
  }
}