Add engines field to function-api package.json requiring Node >=20

Author: Copilot

Custom Apps/boilerplate-typescript-react/function-api/package.json

@@ -30,5 +30,8 @@
     "rimraf": "^5.0.0",
     "typescript": "^4.0.0"
   },
-  "main": "dist/function-api/src/functions/*.js"
+  "main": "dist/function-api/src/functions/*.js",
+  "engines": {
+    "node": ">=20"
+  }
 }