Examine source code of Site Sound

{
  "manifest_version": 2,
  "name": "Site Sound",
  "version": "1.2",
  "description": "Set volume for each website. Remembers your preferred volume per site.",
  "homepage_url": "https://github.com/jicbo/site-sound",
  "icons": {
    "512": "icons/wave-512.png"
  },
  "permissions": [
    "storage",
    "tabs",
    "<all_urls>"
  ],
  "browser_action": {
    "default_icon": "icons/wave-512.png",
    "default_title": "Site Sound",
    "default_popup": "popup/popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "site_sound.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f329decc-333b-4f42-b59c-65e7608928c4}",
      "strict_min_version": "79.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}