added a TestController

src/main/java/com/cs102/attendance/TestController.java

@@ -0,0 +1,13 @@
+package com.cs102.attendance;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class TestController {
+
+    @GetMapping("/hello")
+    public String hello() {
+        return "Spring Boot is working!";
+    }
+}