[RFC] Sentinel Node.js version

## Issue Description

Type: *feature request*

## Describe what feature you want
Implement Node.js version of Sentinel, including but not limited to:

- Basic statistic structure, that is sliding window.
- Rate limiting, the primary function of Sentinel.
- Logging, with little or no outside dependencies to avoid potential package conflicts.
- Extensible metrics interface, that can expose real-time metrics to outside consumer.
- Embedded API server, to expose controlling API or metrics, etc.
- Integrate with Sentinel dashboard, may need machine discovery.

Discussions are welcomed!

No files, tests, or entry points are named. Start by reviewing the existing Sentinel architecture and the scope of each requested Node.js capability, including sliding-window statistics, rate limiting, logging, metrics, API exposure, and dashboard integration. Done would require an agreed design and a complete implementation of the selected scope.

Written by the indexing model from the issue text.