docs: Refreshing GlobalHeader Storybook Example

[williamjstanton]

Summary

Fixes: none

The Storybook example GlobalHeader had some opportunities for improved accessibility.

1. Added accessible Tooltip to icon buttons
2. Replaced old SearchField with Combobox
3. Used AriaLiveRegion to demonstrate screen reader supported CountBadge
4. Updated style packages

Release Category

Documentation, Examples

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Checklist

• MDX documentation adheres to Canvas Kit's Documentation Guidelines
• Label ready for review has been added to PR

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• PR summary describes the change (Fixes/Resolves linked correctly)
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[mannycarrera4]

Although mapping works, we should probably use a render function like in the auto complete example:

{model.state.items.length > 0 && (
                <Combobox.Menu.List cs={styleOverrides.comboboxMenuList}>
                  {item => <Combobox.Menu.Item>{item}</Combobox.Menu.Item>}
                </Combobox.Menu.List>
              )}

[williamjstanton]

I'll need some help with using this model!

[mannycarrera4]

Lets clean up some of the styles and code examples. Content wise it's great! Thank you as always for working through making our documentation better