types: add types to EventEmitter static methods

[suneettipirneni]

Please describe the changes this PR makes and why it should be merged:

Previously the following code:

import { once } from 'node:events';

await client.login(process.env.DISCORD_TOKEN);
const [readyClient] = await once(client, 'ready');

Would improperly type readyClient as any

With this PR the types are properly provided so it resolves to Client<true>

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating