Examine source code of Youtube Audio

{
  "name": "Youtube Audio",
  "version": "2.2",
  "manifest_version": 2,
  "description": "Stream only Audio on Youtube",
  "homepage_url": "https://github.com/themontem/youtube-only-audio",
  "icons": {
    "38": "img/icon38.png",
    "128": "img/icon128.png"
  },
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "permissions": [
    "tabs",
    "webRequest",
    "*://*.googlevideo.com/*",
    "*://*.youtube.com/*",
    "webRequestBlocking",
    "storage"
  ],
  "content_scripts": [
    {
      "all_frames": true,
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "js/content_script.js"
      ],
      "css": [
        "css/content_script.css"
      ],
      "run_at": "document_start"
    }
  ],
  "options_ui": {
    "page": "html/options.html",
    "browser_style": true,
    "chrome_style": true
  },
  "page_action": {
    "browser_style": true,
    "default_icon": {
      "38": "img/disabled_icon38.png"
    },
    "default_title": "Youtube Audio - Disabled",
    "show_matches": [
      "*://*.youtube.com/*"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{db87a5ad-bc92-4840-b7ca-af263c05c90e}"
    }
  }
}