Added an attribute for applying classes to the page-body

Author: fo-code

src/main/resources/bootstrap5/page.jelly

@@ -9,6 +9,10 @@
     <st:attribute name="notitle" use="optional">
       Hide the title on top of the page.
     </st:attribute>
+    <st:attribute name="class" use="optional">
+      Additional classes to be applied to the page body.
+    </st:attribute>
+
   </st:documentation>
 
   <st:header name="Content-Type" value="text/html;charset=UTF-8"/>
@@ -21,7 +25,7 @@
 
       <st:adjunct includes="io.jenkins.plugins.bootstrap5"/>
 
-      <div class="fluid-container">
+      <div class="container-fluid ${class}">
 
         <j:if test="${notitle == null}">
           <h1>${title}</h1>