docs: added more info to global header. Info about where to use the h…

…eader (#206)

lib/src/components/global_header/global_header.dart

@@ -5,6 +5,36 @@ import 'package:flutter/rendering.dart';
 import '../../../zeta_flutter.dart';
 
 /// Global header component
+/// This component should not be used as an appbar in a scaffold.
+/// It can be used in custom scroll views and columns.
+///
+/// ```
+/// SingleChildScrollView(
+///   child: Column(children: [
+///     ZetaGlobalHeader(
+///       title: "Title",
+///       tabItems: childrenOne,
+///       searchBar: ZetaSearchBar(shape: ZetaWidgetBorder.full, size: ZetaWidgetSize.large),
+///       onAppsButton: () {},
+///       actionButtons: [
+///         IconButton(
+///           onPressed: () {},
+///           icon: const ZetaIcon(
+///             ZetaIcons.alert,
+///           ),
+///         ),
+///         IconButton(
+///           onPressed: () {},
+///           icon: const ZetaIcon(
+///             ZetaIcons.help,
+///           ),
+///         ),
+///       ],
+///       avatar: const ZetaAvatar(initials: 'PS'),
+///     ),
+///   ]),
+/// ),
+/// ```
 /// {@category Components}
 ///
 /// Figma: https://www.figma.com/design/JesXQFLaPJLc1BdBM4sisI/%F0%9F%A6%93-ZDS---Components?node-id=1120-26358&node-type=canvas&m=dev