[grade=B] Make website billing production-ready

package.json

@@ -5,10 +5,12 @@
   "type": "module",
   "scripts": {
     "dev": "node --watch src/server.js",
-    "start": "node src/server.js"
+    "start": "node src/server.js",
+    "test": "node --test"
   },
   "dependencies": {
     "express": "^4.21.2",
+    "nodemailer": "^9.0.5",
     "stripe": "^22.0.1"
   }
 }