Examine source code of Smart mute for Firefox

{
  "manifest_version": 3,
  "name": "Smart mute for Firefox",
  "version": "1.0",
  "description": "Mutes all non active tabs",
  "browser_specific_settings": {
    "gecko": {
      "id": "smart.mute.firefox@if.it"
    }
  },
  "icons": {
    "48": "src/icons/mute.png"
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "src/background.js"
    ]
  },
  "options_ui": {
    "page": "src/settings/options.html"
  }
}