fix: update layouts to add hugo.IsMultilingual

- Update layouts/partials/language-selector.html to add
  hugo.IsMultilingual for multilanguage support to hide drop down menu
- Update layours/partials/sidebar.html to add hugo.IsMultilingual to
  hide language icon.

layouts/partials/language-selector.html

@@ -1,4 +1,5 @@
-<div class="lang-dropdown">
+{{ if hugo.IsMultilingual }}
+  <div class="lang-dropdown">
     <select class="lang-select" onchange="location = this.value;">
       {{ $currentLang := .Site.Language.Lang }}
       {{ $siteBase := strings.TrimSuffix "/" .Site.BaseURL }}
@@ -8,4 +9,5 @@
         </option>
       {{ end }}
     </select>
-</div>
+  </div>
+{{ end }}

layouts/partials/sidebar.html

@@ -34,12 +34,15 @@
         </li>
         <!-- .nav-item -->
       {{ end }}
+
+      {{ if hugo.IsMultilingual }}
         <li class="nav-item mt-4">
           <a class="nav-link no-hover">
             <i class="fa-fw fas fa-language"></i>
             {{ partial "language-selector.html" . }}
           </a>
         </li>
+      {{ end }}
     </ul>
   </nav>