room header link추가

client/src/components/Room/RoomHeader.js

+import { Link } from "react-router-dom";
+
 const RoomHeader = () => {
   return (
     <div className="container">
@@ -25,6 +27,7 @@ const RoomHeader = () => {
           <p className="m-2" style={{ fontWeight: "bold", fontSize: "20px" }}>
             회의
           </p>
+          <Link to="/user">
             <button
               type="button"
               className="m-2 rounded"
@@ -38,6 +41,7 @@ const RoomHeader = () => {
             >
               돌아가기
             </button>
+          </Link>
         </div>
       </div>
     </div>