Alternative TypeScript-based orchestrator

While the current data explorer / front-end is implemented as a Java Spring app, we understand many prototyping and development teams prefer to work in JavaScript/TypeScript.

The interfaces in [cdk/lib/orchestrators/base.ts](https://github.com/aws-samples/query-structured-data-with-amazon-bedrock/blob/main/cdk/lib/orchestrators/base.ts) have been deliberately standardised to support expanding this sample with alternative orchestrator/client layers in future. It'd be great to hear feedback (or even see PRs!) on what users would find most relevant for a JS/TS option. We have a partial draft in Next.js + React already, but haven't been able to tidy it up for publication yet.