fix(sidebar): use a dropdown for archive

Fixes #12
Fixes #13

components/sidebar/archives.php

@@ -1,12 +1,9 @@
 <div class="card card-primary">
   <div class="card-header"><i class="fa fa-folder"></i> Archives</div>
-  <div class="card-menu">
-    <?php
-      wp_get_archives( array(
-        'type' => 'yearly',
-        'echo' => 1,
-        'order'=> 'ASC'
-      ) );
-      ?>
+  <div class="card-body">
+    <select class="card-select" name="archive-dropdown" onChange='document.location.href=this.options[this.selectedIndex].value;'>
+      <option value=""><?php echo attribute_escape(__('Selection d\'une année…')); ?></option>
+      <?php wp_get_archives('type=yearly&format=option&show_post_count=1'); ?>
+    </select>
   </div>
 </div>