Fix spelling mistake

Author: lulunac27a

index.html

@@ -12,7 +12,7 @@ <h1>Rate Our Service</h1>
             <span class="star" data="4" onclick="changeRating(4)">&#9733;</span>
             <span class="star" data="5" onclick="changeRating(5)">&#9733;</span>
         </div>
-        <button type="sumbit" id="submit-button">Submit Rating</button>
+        <button type="submit" id="submit-button">Submit Rating</button>
         <div id="rating-output"></div>
         <script src="main.js"></script>
     </body>