Examine source code of Env Switcher

{
  "manifest_version": 2,
  "name": "Env URL Switcher",
  "version": "1.0",
  "permissions": [
    "activeTab",
    "storage"
  ],
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "env-switcher@portales.dev"
    }
  },
  "browser_action": {
    "default_icon": {
      "16": "images/16.png",
      "48": "images/48.png",
      "128": "images/128.png"
    },
    "default_title": "Env URL Switcher"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "icons": {
    "16": "images/16.png",
    "48": "images/48.png",
    "128": "images/128.png"
  }
}