Examine source code of Tab Router

{
  "manifest_version": 2,
  "name": "Tab Router",
  "version": "0.2.1",
  "description": "Routes new tabs to windows by URL context, or opens a new window",
  "browser_specific_settings": {
    "gecko": {
      "id": "tab-router@firefox",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  },
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}