How to implement async event tracking in JS runtime without blocking RPC response?

[mengxin]

base on this discussion:

registerBeforeEvent and registerAfterEvent

I think there’s some confusion. Emitting new events, can be done via the client API or the provided runtime functions (in any runtime). If you register before/after hooks, they will only fire if the REST API /v2/event path receives a new event to emit, they will not if you use the runtime function inside a custom RPC. To process events, you need to register a function that will fire asynchronously on emitted events. This function can only be registered in the Go runtime.