Add TypeScript types for handlers

**Feature request**
It would be great to have monitoring for lib.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_monitoring` with default `false`.

Start by checking the lib directory and the existing configuration entry points. The title asks for TypeScript handler types, while the body proposes monitoring and an enable_monitoring option, so clarify which request is intended before locating tests. Done should include an agreed scope and verification that the option defaults to false.

Written by the indexing model from the issue text.