Examine source code of Mute Unfocused Tabs

{
  "author": "igorlogius",
  "homepage_url": "https://github.com/igorlogius/webextensions/tree/main/mute-unfocused-tabs",
  "description": "Only let the focused tab be audible",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_area": "navbar",
    "default_icon": "icon.png"
  },
  "icons": {
    "320": "icon.png"
  },
  "manifest_version": 2,
  "name": "Mute Unfocused Tabs",
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "tabs",
    "storage",
    "menus"
  ],
  "version": "1.4.24",
  "browser_specific_settings": {
    "gecko": {
      "id": "{6d23aa83-a3f8-4c84-b146-486a92a09f5e}"
    }
  }
}