Examine source code of YouTube row fixer

{
  "manifest_version": 2,
  "name": "YouTube row fixer",
  "version": "2.3.5",
  "homepage_url": "https://github.com/RootOperator/YouTube-row-fixer",
  "applications": {
    "gecko": {
      "id": "{528dea52-7c0b-43a6-b899-85e7952022c3}"
    }
  },
  "description": "decide how many videos you want on one row",
  "permissions": [
    "activeTab",
    "storage"
  ],
  "icons": {
    "64": "icons/icon.png"
  },
  "browser_action": {
    "default_icon": "icons/icon.png",
    "default_title": "YouTube Row Fix",
    "default_popup": "menu/index.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "background.js"
      ],
      "run_at": "document_end"
    }
  ]
}