Examine source code of Umbraco DevTools

{
  "manifest_version": 3,
  "name": "Umbraco DevTools",
  "description": "A browser extension to help with debugging the Webcomponent based Umbraco backoffice V13+",
  "version": "0.0.1",
  "browser_specific_settings": {
    "gecko": {
      "id": "umbraco.devtools@warrenbuckley.co.uk"
    }
  },
  "icons": {
    "16": "icons/icon-16.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png",
    "256": "icons/icon-256.png"
  },
  "action": {
    "default_icon": {
      "16": "icons/icon-grayscale-16.png",
      "48": "icons/icon-grayscale-48.png",
      "128": "icons/icon-grayscale-128.png",
      "256": "icons/icon-grayscale-256.png"
    },
    "default_popup": "popup-not-found.html"
  },
  "devtools_page": "devtools-registration.html",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "js": [
        "content.js"
      ],
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_end"
    }
  ]
}