Examine source code of ytrtlfix

{
  "manifest_version": 2,
  "name": "ytrtlfix",
  "version": "1.0",
  "description": "Fix Youtube menu when display language is right to left",
  "icons": {
    "100": "icons/icon100.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*"
      ],
      "js": [
        "ytrtlfix.js"
      ]
    }
  ]
}