docs(persister): document asynchronous serialization callbacks - #11411

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: nrwl/nx-set-shas@3e9ad7370203c1e93d109be57f3b72eb0eb511b1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/