Examine source code of Last-Modified Detective

{
  "manifest_version": 2,
  "name": "Last-Modified Detective",
  "version": "1.5",
  "description": "Find out when a page was really last updated. Reads the server's Last-Modified header and shows the date plus how long ago it was, along with other response headers, and jumps to the Wayback Machine.",
  "icons": {
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "64": "icons/icon-64.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{16bc40e1-03b8-4c6b-b759-e876517b8769}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "activeTab",
    "<all_urls>"
  ],
  "browser_action": {
    "default_title": "Last-Modified Detective",
    "default_popup": "src/popup.html",
    "default_icon": {
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png",
      "64": "icons/icon-64.png"
    }
  }
}