added notificationDTO

src/notifications/notification.dto.ts

+import { IsString, Length, IsUUID, IsIn } from 'class-validator';
+
+export class NotificationdDTO {
+  // alert is for serious messages, note is for smaller updates on a situation
+  @IsIn(['alert', 'note'])
+  type: string;
+  @IsString()
+  @Length(0, 63)
+  message: string;
+  @IsUUID('4')
+  game: string;
+}