feat(server): add test /test endpoint (#380)

* feat(server): add test /test endpoint

* fix lint

Author: chloezxyy

apps/server/src/app.controller.ts

@@ -1,8 +1,13 @@
-import { Controller } from '@nestjs/common';
+import { Controller, Get } from '@nestjs/common';
 
 import { AppService } from './app.service';
 
 @Controller('test')
 export class AppController {
   constructor(private readonly appService: AppService) {}
+
+  @Get()
+  async sayHello() {
+    return 'Hello World!';
+  }
 }