Examine source code of Currentcy

{
  "manifest_version": 2,
  "name": "Currentcy",
  "version": "1.15resigned1",
  "description": "Currentcy automatically converts foreign currencies into the local one (set in Options). Rate values are updated every thirty minutes using a free API (https://free.currencyconverterapi.com/ ). Please note that this project is in beta phase, so there may be bugs. The source code is available on GitHub: https://github.com/tehw0lf/currentcy",
  "background": {
    "scripts": [
      "currentcy.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "convert.js"
      ],
      "run_at": "document_end"
    }
  ],
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "https://free.currencyconverterapi.com/*",
    "webRequest",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{658cd452-a70d-4b3a-8a5f-d99a84cf666e}"
    }
  }
}