Add multiple="multiple" to Forms => Selects as described in explanation

docs/base-css.html

@@ -1047,7 +1047,7 @@ For example, <code>section</code> should be wrapped as inline.
               <option>5</option>
             </select>
             <br>
-            <select>
+            <select multiple="multiple">
               <option>1</option>
               <option>2</option>
               <option>3</option>
@@ -1064,7 +1064,7 @@ For example, &lt;code&gt;section&lt;/code&gt; should be wrapped as inline.
   &lt;option&gt;5&lt;/option&gt;
 &lt;/select&gt;
 
-&lt;select&gt;
+&lt;select multiple="multiple"&gt;
   &lt;option&gt;1&lt;/option&gt;
   &lt;option&gt;2&lt;/option&gt;
   &lt;option&gt;3&lt;/option&gt;

docs/templates/pages/base-css.mustache

@@ -984,7 +984,7 @@
               <option>5</option>
             </select>
             <br>
-            <select>
+            <select multiple="multiple">
               <option>1</option>
               <option>2</option>
               <option>3</option>
@@ -1001,7 +1001,7 @@
   &lt;option&gt;5&lt;/option&gt;
 &lt;/select&gt;
 
-&lt;select&gt;
+&lt;select multiple="multiple"&gt;
   &lt;option&gt;1&lt;/option&gt;
   &lt;option&gt;2&lt;/option&gt;
   &lt;option&gt;3&lt;/option&gt;