Examine source code of Tab Icon Swap

{
  "manifest_version": 3,
  "name": "__MSG_extensionName__",
  "version": "1.0",
  "description": "__MSG_extensionDescription__",
  "icons": {
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e2d0b3a9-c1e8-0f2c-a0d8-b3e1f0b5c1a2}",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "collects_data": false
      }
    }
  },
  "permissions": [
    "storage",
    "scripting",
    "activeTab"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "128": "icons/icon128.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ]
}