Fix Serbia Language (#822)

* Fix Serbia Language

* Rename messages_sr_Latn_RS.properties to messages_sr_LATN_RS.properties

* Update languages.html

* Update README.md

src/main/resources/templates/fragments/navbar.html

@@ -139,7 +139,6 @@
                       <!-- Dropdown items will be added here by JavaScript -->
                     </div>
                   </li>
-                  <script src="js/languageSelection.js"></script>
                   <li class="nav-item">
                     <a class="nav-link" id="dark-mode-toggle" href="#">
                       <img class="navbar-icon" id="dark-mode-icon" src="moon.svg" alt="icon" />