[QUESTION]是否支持限流事件监听

## Issue Description
Sentinel 当前支持对熔断事件的监听，通过 `EventObserverRegistry ` 可以实现，查看文档之后并没有发现对限流事件的监听。请问当前是否支持对限流事件的监听？

Start with the Sentinel documentation and the EventObserverRegistry API mentioned in the issue, then inspect the rate-limiting event handling entry points and related tests if they are present. Done means determining from the current code and documentation whether rate-limiting event listening is supported and recording the answer or a concrete implementation gap.

Written by the indexing model from the issue text.