Add TypeScript types for config

**Feature request**
It would be great to have caching for helpers.

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

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

The issue names TypeScript config types and an `enable_caching` option, but does not identify files or tests. First locate the config definition and its TypeScript type declarations, then determine whether the requested work is limited to typing the option or also requires implementing helper caching. Done should include a default of `false` and coverage for the intended behavior.

Written by the indexing model from the issue text.