Examine source code of Sego's Roblox

{
  "name": "Sego's Roblox",
  "version": "1.0.0",
  "description": "Extension to customize roblox.com",
  "manifest_version": 2,
  "author": "Sego",
  "browser_specific_settings": {
    "gecko": {
      "id": "segorbx@sego.app"
    }
  },
  "browser_action": {
    "default_popup": "settings.html"
  },
  "options_ui": {
    "page": "settings.html"
  },
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.roblox.com/*",
        "https://web.roblox.com/*"
      ],
      "js": [
        "sego.js"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "16": "icon/16.png",
    "32": "icon/32.png",
    "48": "icon/48.png",
    "128": "icon/128.png"
  }
}