fix(Gateway): Export interface (#10060)

* fix(types): export missing `Gateway` interface

* docs(Gateway): update link to `WebSocketManager`

packages/core/src/Gateway.ts

@@ -2,6 +2,11 @@ import type { Awaitable } from '@discordjs/util';
 import type { ManagerShardEventsMap, WebSocketShardEvents } from '@discordjs/ws';
 import type { GatewaySendPayload } from 'discord-api-types/v10';
 
+/**
+ * Gateway-like structure that can be used to interact with an actual WebSocket connection.
+ * You can provide a custom implementation, useful for running a message broker between your app and your gateway,
+ * or you can simply use the {@link @discordjs/ws#(WebSocketManager:class)}.
+ */
 export interface Gateway {
 	getShardCount(): Awaitable<number>;
 	on(

packages/core/src/index.ts

@@ -1,5 +1,6 @@
 export * from './api/index.js';
 export * from './client.js';
+export * from './Gateway.js';
 export * from './util/index.js';
 
 export * from 'discord-api-types/v10';