Examine source code of ZenTube

{
  "description": "Zen mode for YouTube",
  "manifest_version": 2,
  "name": "ZenTube",
  "version": "1.1.4",
  "author": "surajsharma",
  "homepage_url": "https://evenzero.in",
  "icons": {
    "144": "icons/favicon4_144.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "browser-polyfill.js",
        "defaultSettings.js",
        "contentscript.js",
        "emoji.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_action": {
    "default_icon": "icons/favicon4_144.png",
    "default_title": "Zen Mode for Youtube",
    "default_popup": "options/options.html"
  },
  "permissions": [
    "storage",
    "tabs",
    "scripting",
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{1761af7a-a12c-455b-9728-557f5d9c4b98}"
    }
  }
}