Examine source code of TabGain — Volume Booster

{
  "manifest_version": 2,
  "name": "TabGain — Volume Booster",
  "version": "1.0.0",
  "description": "Boost quiet audio up to 600% with independent volume controls for each Firefox tab.",
  "icons": {
    "48": "icons/volume.svg",
    "96": "icons/volume.svg"
  },
  "permissions": [
    "sessions",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_icon": "icons/volume.svg",
    "default_title": "TabGain — Volume Booster",
    "default_popup": "popup/popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "audio-controller.js",
        "content.js"
      ],
      "run_at": "document_start",
      "all_frames": true,
      "match_about_blank": true
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "tab-volume-booster@local.extension",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}