Examine source code of Try XPath

{
  "name": "Try XPath",
  "description": "This add-on displays the result of evaluating XPath expression or CSS selector.",
  "manifest_version": 2,
  "version": "1.3.5",
  "icons": {
    "48": "icons/icon_48.png"
  },
  "applications": {
    "gecko": {
      "id": "{ba6bb880-bcbe-4792-a020-fcfab8d67027}",
      "strict_min_version": "53.0"
    }
  },
  "permissions": [
    "<all_urls>",
    "storage"
  ],
  "background": {
    "scripts": [
      "scripts/try_xpath_functions.js",
      "background/try_xpath_background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/icon_48.png",
    "default_title": "Try XPath",
    "default_popup": "popup/popup.html"
  },
  "web_accessible_resources": [],
  "content_scripts": [],
  "options_ui": {
    "page": "/pages/options.html"
  }
}