doc: add note about AsyncResource for Worker pooling

When implementing a pool for Worker threads, the correlation between
posting tasks and getting their results may get lost, depending on
the implementation.

The `AsyncResource` API is the primary way to solve that issue,
so link it from the recommendation in the worker docs.

(This was brought up at the collaborator summit in Berlin.)

PR-URL: https://github.com/nodejs/node/pull/28023


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>