[Feat] Use type-safe EventEmitter interface

[jonahsnider]

This replaces the SharderEvents enum with an object type that maps event names to listener function signatures. In combination with the TypedEventEmitter interface from @pizzafox/util this means TypeScript users get automatic type-checking of their event listeners, and the library gets safe calls to emit.

In fact, implementing this revealed 2 non-compliant ShardingManager#emit usages:

Kurasuta/src/IPC/MasterIPC.ts

Lines 62 to 66 in 16a2cfb

	private _shardready(message: NodeMessage) {
	const { d: { shardID } } = message.data;
	this._debug(`Shard ${shardID} became ready`);
	this.manager.emit(SharderEvents.SHARD_READY, shardID);
	}

Kurasuta/src/IPC/MasterIPC.ts

Lines 68 to 72 in 16a2cfb

	private _shardreconnect(message: NodeMessage) {
	const { d: { shardID } } = message.data;
	this._debug(`Shard ${shardID} tries to reconnect`);
	this.manager.emit(SharderEvents.SHARD_RECONNECT, shardID);
	}

Adding the dependency will slightly increase bundle size, even though it's just used at build-time for TypeScript users. The official recommendation is to list it in the dependencies field of package.json.

In its current state this PR is a breaking change since SharderEvents is no longer an enum. This could easily be changed back to an enum and rename the new type to something like SharderEventListeners.

[DevYukine]

This seems interesting, i will have a look on the weekend at it 👍