Examine source code of Devil Debugger

{
  "manifest_version": 2,
  "name": "Devil Debugger",
  "version": "2.0.0",
  "author": "Vignesh Miller",
  "description": "A hell-precise visual debugger for the web. Outline every element by tag, nesting depth or mono color, and inspect any node live — tag, id, classes and box size — without leaving the page.",
  "permissions": [
    "tabs",
    "storage",
    "<all_urls>"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Devil Debugger — toggle visual debugging",
    "default_icon": {
      "128": "icons/128.png"
    }
  },
  "icons": {
    "128": "icons/128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "shared-data.js",
        "content.js"
      ],
      "run_at": "document_idle",
      "all_frames": false
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "starvicki2002@gmail.com",
      "strict_min_version": "91.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}