added link to username changing page

views/user.html

@@ -24,6 +24,8 @@
         <br>
         <button onclick="location.assign('/changePW')">Want to change your password?</button>
         <br>
+        <button onclick="location.assign('/changeUsername')">Want to change your username?</button>
+        <br>
         <button onclick="location.assign('/posts')">Want to chat with some cool fellas?</button>
       </div>
   </main>