create Header.js

+import React from "react";
+import Styled from "styled-components";
+
+const Header = Styled.div`
+    width: 100%;
+    display: flex;
+    justify-content: center;
+    margin: 10px 0px;
+    font-size: 25px;
+`;
+
+export default () => {
+  return (
+    <Header>
+      <h1>KHU Chatting service</h1>
+    </Header>
+  );
+};