Examine source code of Speedify

{
  "manifest_version": 2,
  "name": "Speedify",
  "version": "2.0",
  "description": "Adds more speed rates on video playbacks.",
  "icons": {
    "48": "icons/speed-48.png",
    "96": "icons/speed-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "thirdParty/jquery-3.5.1.slim.min.js",
        "speedify.js"
      ]
    }
  ]
}