Examine source code of SendSMSFree

{
  "manifest_version": 2,
  "name": "SendSMSFree",
  "version": "0.6resigned1",
  "description": "Envoyer un SMS avec l'API de Free Mobile (free.fr)",
  "developer": {
    "name": "GTeam",
    "url": "https://framagit.org/GTeam/SendSMSFree"
  },
  "icons": {
    "48": "icons/sms-48.png",
    "96": "icons/sms-96.png"
  },
  "applications": {
    "gecko": {
      "id": "SendSMSFree@gteam.fr",
      "strict_min_version": "45.0"
    }
  },
  "permissions": [
    "activeTab",
    "*://smsapi.free-mobile.fr/*",
    "notifications",
    "storage"
  ],
  "browser_action": {
    "default_icon": {
      "16": "icons/sms-16.png",
      "19": "icons/sms-19.png",
      "32": "icons/sms-32.png",
      "38": "icons/sms-38.png",
      "48": "icons/sms-48.png",
      "64": "icons/sms-64.png"
    },
    "browser_style": true,
    "default_title": "Envoyer un SMS avec Free Mobile",
    "default_popup": "popup/sms.html"
  },
  "options_ui": {
    "page": "options/options.html",
    "browser_style": true
  }
}