fix(useWebSocket): don't hide pong setTimeout reference

[kellerza]

Description

In #2170 the capability was added to monitor pong's (or server replies) as part of the existing heartbeat/ping functionality.

Currently if the pong gets delayed/dropped for any reason (e.g. server restart) and "pong reply time">pingInterval; the ping function would execute again

The ping function creates a pong setTimout and saves the reference (this timeout will close the connection if allowed to expire).

If a previous setTimeout has not been cancelled yet, the reference is lost and the connection will be closed.

Additional context

By adjusting the timers appropriately you can now be more leanient and allow for "dropped" pongs. E.g if you require 1 pong (or server message) for every 3 pings you could set pongTimeout >= 3x ping interval

It's ok to clear and invalid setTimeout reference - https://developer.mozilla.org/en-US/docs/Web/API/clearTimeout#notes

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What is the purpose of this pull request?

• Bug fix feat(useWebSocket): enhence heartbeat #2170
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines.
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• Ideally, include relevant tests that fail without this PR but pass with it.

[antfu]

I think we'd better use undefined than 0

[kellerza]

Anything still missing here?