Add handlebars;

package.json

@@ -20,6 +20,7 @@
   "homepage": "https://github.com/detleph/server#readme",
   "dependencies": {
     "@prisma/client": "^3.3.0",
+    "@types/handlebars": "^4.1.0",
     "@types/jsonwebtoken": "^8.5.5",
     "@types/mjml": "^4.7.0",
     "@types/node": "^16.10.3",
@@ -28,6 +29,7 @@
     "argon2": "^0.28.2",
     "dotenv": "^10.0.0",
     "express": "^4.17.1",
+    "handlebars": "^4.7.7",
     "jsonwebtoken": "^8.5.1",
     "mjml": "^4.11.0",
     "nodemailer": "^6.7.0",