fix: make header optional

Author: FabienMotte

examples/react/css/src/Panel.tsx

@@ -1,16 +1,18 @@
 import React from 'react';
 
 type PanelProps = React.PropsWithChildren<{
-  header: string;
+  header?: React.ReactNode;
   footer?: React.ReactNode;
 }>;
 
 export function Panel({ header, children, footer }: PanelProps) {
   return (
     <div className="ais-Panel">
-      <div className="ais-Panel-header">
-        <span>{header}</span>
-      </div>
+      {Boolean(header) && (
+        <div className="ais-Panel-header">
+          <span>{header}</span>
+        </div>
+      )}
       <div className="ais-Panel-body">{children}</div>
       {Boolean(footer) && <div className="ais-Panel-footer">{footer}</div>}
     </div>