Examine source code of SoundTuner

{
  "manifest_version": 2,
  "name": "SoundTuner",
  "version": "1.3.3",
  "author": "Abhinav Neelam",
  "description": "Extension to manipulate background sounds. Can lower/increase volume, add pan and mono. Can also save background sounds per website for future visits.",
  "homepage_url": "https://github.com/LoneCoder21/SoundTuner",
  "icons": {
    "48": "icon.png",
    "96": "icon.png"
  },
  "action": {
    "default_icon": "icon.png",
    "default_title": "SoundTuner",
    "default_popup": "popup.html"
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "SoundTuner",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "browser-polyfill.js",
        "content.js"
      ],
      "all_frames": true,
      "match_about_blank": true,
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "inject.js"
  ],
  "permissions": [
    "activeTab",
    "storage",
    "unlimitedStorage",
    "notifications",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "browser-polyfill.js",
      "background.js"
    ]
  },
  "host_permissions": [
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{0213c12a-0059-4b78-926b-687979e37ad8}"
    }
  }
}