Examine source code of FlowControl

{
  "manifest_version": 2,
  "name": "FlowControl",
  "version": "1.1.1",
  "description": "Manage speed of youtube videos with shortcuts",
  "homepage_url": "https://github.com/mdn/webextensions-examples/tree/main/beastify",
  "icons": {
    "48": "48f.png",
    "64": "flow.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "flowjs.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{4c51b447-2c91-4385-936b-e93372de930e}"
    }
  }
}