Examine source code of Roblox Dark Theme

{
  "manifest_version": 2,
  "name": "Roblox Dark Theme",
  "version": "1.0",
  "description": "Provides a dark theme for roblox.com",
  "icons": {
    "48": "icons/48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "exceptionalgains@gmail.com"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.roblox.com/*"
      ],
      "js": [
        "theme.js"
      ]
    }
  ]
}