Examine source code of Make YouTube Red Again

{
  "manifest_version": 2,
  "name": "Make YouTube Red Again",
  "version": "1.0",
  "description": "Changes the YouTube progress bar back to red",
  "license": "Unlicense",
  "homepage_url": "https://github.com/desonov/make-youtube-red-again",
  "icons": {
    "48": "icon.svg"
  },
  "permissions": [],
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "css": [
        "styles.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{1ee967f2-72ef-4a39-816d-4c1cccabc87d}"
    }
  }
}