Examine source code of Calcy

{
  "manifest_version": 2,
  "name": "Calcy",
  "version": "1.0",
  "description": "Does simple calculations",
  "browser_action": {
    "default_icon": "icons/icon.png",
    "default_title": "Calcy",
    "default_popup": "index.html"
  },
  "icons": {
    "48": "icons/icon.png"
  },
  "content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self';"
}