Examine source code of Per-Tab Volume Memory

{
  "manifest_version": 2,
  "name": "Per-Tab Volume Memory",
  "version": "1.0",
  "description": "Remember volume per tab/domain automatically.",
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "per-tab-volume-memory@amo",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "128": "icon.png"
  }
}