IrcConnection type should inherit from net.Socket

[aabluedragon]

Latest commits to master expose only a few properties in IrcConnection, even though the value in ircClient.conn actually refers to a subtype of net.Socket.
As a result, this is causing issues because many important properties/functions are no longer available in ircClient.conn, such as destroyed, and the write function only accepts string instead of also the Buffer type.
To work around this issue temporary, I replaced these 2 type declarations:

import { Socket } from 'net';
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.
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export type IrcConnectionEventEmitter = Socket;
export interface IrcConnection extends IrcConnectionEventEmitter {}