[Feature] Add a local development kit for contributors

[Gezi-lzq]

Motivation

I recently started contributing to Fluss. The build process is clear and the documentation is comprehensive, while most existing guides focus on deployment and usage scenarios. After changing code, running locally built artifacts and validating Flink or lake tiering still requires manually combining several services, configurations, and dependencies.

I am also exploring using coding agents to start environments and validate test cases, which benefits from a stable, clear, and repeatable local interface.

Solution

I put together a DevKit based on Docker Compose and just. It mounts the local build-target, manages integration environments through profiles, and provides composable commands for startup and validation.

The DevKit focuses on source development and local validation, alongside the existing quickstarts and deployment guides. A Draft PR provides a working implementation for discussion. Feedback on the direction, tool choice, and maintenance scope would be appreciated.

I am willing to submit a PR.