Lock focus to pinned tab

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Lock focus to pinned tab",
  "description": "固定されたタブからフォーカスが移動しないようにします。",
  "version": "0.3",
  "background": {
    "persistent": true,
    "scripts": [
      "event.js"
    ]
  }
}