docs: update example

Author: mrholek

docs/content/components/sidebar.md

@@ -44,7 +44,7 @@ Below is an sidebar example that is shown by default on desktop devices.
   <ul class="sidebar-nav">
     <li class="nav-title">Nav Title</li>
     <li class="nav-item">
-      <a class="nav-link" href="#">
+      <a class="nav-link active" href="#">
         <i class="nav-icon cil-speedometer"></i> Nav item
       </a>
     </li>
@@ -186,7 +186,7 @@ Change the appearance of sidebars with the `.sidebar-dark` class.
   <ul class="sidebar-nav">
     <li class="nav-title">Nav Title</li>
     <li class="nav-item">
-      <a class="nav-link" href="#">
+      <a class="nav-link active" href="#">
         <i class="nav-icon cil-speedometer"></i> Nav item
       </a>
     </li>