Examine source code of Surge

{
  "manifest_version": 2,
  "name": "Surge Download Manager",
  "description": "High-performance download acceleration. Intercepts and routes browser downloads to Surge's multi-connection engine.",
  "version": "2.1.1",
  "permissions": [
    "downloads",
    "storage",
    "notifications",
    "webRequest",
    "http://127.0.0.1/*",
    "<all_urls>"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "browser_specific_settings": {
    "gecko": {
      "id": "surge@surge-downloader.com",
      "strict_min_version": "109.0"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "Surge",
    "default_popup": "popup.html"
  }
}