Examine source code of Battery Status Plus

{
  "name": "Battery Status",
  "version": "3.0.1",
  "author": "Guokai Han",
  "manifest_version": 2,
  "minimum_chrome_version": "118",
  "description": "Display battery level, charging or discharging status.",
  "default_locale": "en",
  "offline_enabled": true,
  "permissions": [
    "alarms",
    "background",
    "offscreen",
    "storage"
  ],
  "optional_permissions": [
    "notifications"
  ],
  "icons": {
    "16": "icon/16.png",
    "48": "icon/48.png",
    "128": "icon/128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "browser_action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3f6d0e23-be46-438c-a07e-d485756b4dc6}"
    }
  }
}