Add gateway import way

It adds the way the user can import the file in case of a manual creation, so that it doesn't get lost in the process.

Author: AndersonAlpin

content/websockets/gateways.md

@@ -53,6 +53,19 @@ handleEvent(data) {
 
 > info **Hint** `@SubscribeMessage()` and `@MessageBody()` decorators are imported from `@nestjs/websockets` package.
 
+Once the gateway is created, we can import it into our module.
+
+```typescript
+import { Module } from '@nestjs/common';
+import { EventsGatway } from './events.gateway';
+
+@@filename(events.module)
+@Module({
+  providers: [EventsGatway]
+})
+export class EventsModule {}
+```
+
 You can also pass in a property key to the decorator to extract it from the incoming message body:
 
 ```typescript