Examine source code of YT Speed Change

{
  "manifest_version": 2,
  "name": "YT Speed Change",
  "short_name": "Speed Change",
  "version": "1.0.5.3",
  "description": "Save time by changing the playback speed of YouTube at well.",
  "icons": {
    "16": "image/icon16.png",
    "48": "image/icon48.png",
    "128": "image/icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*",
        "https://m.youtube.com/*"
      ],
      "js": [
        "main.js"
      ],
      "css": [
        "main.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{ff947607-7ec1-410e-99ed-6088e12df7b1}"
    }
  }
}