Fix description preview and syntax highlighting

core/src/main/resources/lib/form/textarea.jelly

@@ -73,7 +73,7 @@ THE SOFTWARE.
   <j:set var="value" value="${attrs.value ?: instance[attrs.field] ?: attrs.default}" />
   <j:if test="${attrs['codemirror-mode']!=null}">
     <st:adjunct includes="
-        lib.form.textarea.textarea
+        lib.form.textarea.textarea,
         org.kohsuke.stapler.codemirror.mode.${attrs['codemirror-mode']}.${attrs['codemirror-mode']},
         org.kohsuke.stapler.codemirror.theme.default"/>
   </j:if>