Fixes #14296: document a table caption example

docs/_includes/css/tables.html

@@ -5,6 +5,7 @@
   <p>For basic styling&mdash;light padding and only horizontal dividers&mdash;add the base class <code>.table</code> to any <code>&lt;table&gt;</code>. It may seem super redundant, but given the widespread use of tables for other plugins like calendars and date pickers, we've opted to isolate our custom table styles.</p>
   <div class="bs-example">
     <table class="table">
+      <caption>Optional table caption.</caption>
       <thead>
         <tr>
           <th>#</th>