[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!