Examine source code of Production Warning Banner

{
  "manifest_version": 2,
  "name": "Production Warning Banner",
  "version": "2.1",
  "description": "Displays a configurable banner on your production environments",
  "browser_specific_settings": {
    "gecko": {
      "id": "prod-warning@ct1735x.fr",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Production Warning"
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ]
}