Examine source code of Push to Kindle

{
  "name": "Push to Kindle",
  "version": "2.6.6",
  "manifest_version": 3,
  "description": "Send web articles to your Kindle",
  "action": {
    "default_title": "Push to Kindle",
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png",
      "128": "icon128.png"
    },
    "default_area": "navbar"
  },
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "activeTab",
    "scripting"
  ],
  "commands": {
    "_execute_action": {
      "suggested_key": {
        "default": "Alt+Shift+K"
      }
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "jid0-GokC6R49cBZciOKniufAR4QKFWc@jetpack",
      "strict_min_version": "102.0"
    }
  }
}