Examine source code of Per-Tab Volume Slider

{
  "manifest_version": 2,
  "name": "Per-Tab Volume Slider v2",
  "version": "1.1",
  "description": "Volume slider per tab, synced with site volume, RTL/LTR aware.",
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_script.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "icons": {
    "48": "icons/volume-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c7630e4c-8799-4a49-9cd9-f9599f86e091}"
    }
  }
}