Examine source code of Subdomain Center

{
  "manifest_version": 2,
  "name": "Subdomain Center",
  "version": "1.1",
  "description": "A.R.P. Syndicate's Subdomain Center Browser Extension downloads a list of subdomains for the website you're on.",
  "permissions": [
    "activeTab",
    "downloads",
    "https://api.subdomain.center/"
  ],
  "background": {
    "scripts": [
      "background.js",
      "psl.js"
    ]
  },
  "icons": {
    "64": "icon.png"
  },
  "browser_action": {
    "default_title": "Subdomain Center",
    "default_icon": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "subdomain_center@io.arpsyndicate"
    }
  }
}