Expose event to handle server-issued disconnects

[mat1jaczyyy]

A client can be disconnected by the server due to various reasons, including regular TETR.IO maintenance, which poses a problem for long-running bots.

Expose an event to notify bots when they've been disconnected and why, allowing them to handle reconnecting and re-setting up any bot state / in-game actions (such as opening rooms) themselves upon successful reconnection.

[mat1jaczyyy]

Note: a hotfix was already applied to seemingly random ws closes here:

tetr.js/src/ws/WebSocketManager.ts

Lines 166 to 168 in 4ceff0b

	this.socket.on("close", () => {
	this.connect(true); // i guess temporary fix on silent disconnect
	});

I'm not sure if these are just random disconnects due to long idle periods, or the ws just closes silently upon maintenance.

[Sup3rFire]

Fixed

[mat1jaczyyy]

if there is no apparent reason for a disconnect (nothing happened on the ribbon, ws just closed itself), can this also be raised as an event rather than just silently reconnecting?