Examine source code of FiReTC

{
  "manifest_version": 2,
  "name": "FireTC for RTC Nomade",
  "short_name": "FireTC",
  "description": "Get the realtime delay before the next RTC bus arrives.",
  "version": "1.0.6",
  "homepage_url": "https://github.com/jebeaudet/ChRomeTC",
  "icons": {
    "16": "img/bus_16x16.png",
    "32": "img/bus_32x32.png",
    "48": "img/bus_48x48.png",
    "128": "img/bus_128x128.png"
  },
  "web_accessible_resources": [
    "fonts/*.woff2"
  ],
  "browser_action": {
    "default_icon": "img/bus_512x512.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "storage"
  ],
  "content_security_policy": "connect-src https://wssiteweb.rtcquebec.ca; default-src 'self'"
}