Add pdflib package

Author: HugoGresse

functions/package-lock.json

@@ -29,6 +29,7 @@
         "firebase-admin": "^11.11.0",
         "firebase-functions": "^4.5.0",
         "luxon": "^3.4.4",
+        "pdf-lib": "^1.17.1",
         "puppeteer": "^24.10.1",
         "ts-custom-error": "^3.3.1",
         "uuid": "^9.0.1"