Examine source code of YouTube Quality Setter

{
  "manifest_version": 3,
  "name": "YouTube Quality Setter",
  "version": "1.0",
  "browser_specific_settings": {
    "gecko": {
      "id": "yt-quality-setter@yourj4m.github.io"
    }
  },
  "description": "Sets the desired quality on YouTube videos. Nothing else.",
  "homepage_url": "https://github.com/yourj4m/YT_Quality_Setter",
  "permissions": [
    "storage",
    "tabs"
  ],
  "action": {
    "default_popup": "popup/choose_quality.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "icons": {
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "yt_quality_setter.js"
      ]
    }
  ]
}