chore(dropdown): add split button action example

[Mash707]

Closes #10197
References:

• https://v5-archive.patternfly.org/components/menus/dropdown/react-deprecated#split-button-checkbox
• https://www.patternfly.org/components/menus/menu-toggle#split-toggle-with-checkbox

[Mash707]

@kmcfaul @thatblindgeye I have created a draft for the example. Let me know of the changes required.
Also could you guys also suggest the description and sub heading for the example, I am not sure of it. Thank You

[patternfly-build]

Preview: https://patternfly-react-pr-11753.surge.sh

A11y report: https://patternfly-react-pr-11753-a11y.surge.sh

[Mash707]

There were some a11y issues regarding MenuToggle and MenuToggleCheckbox since I didn't add aria-label to them.
@thatblindgeye do check the aria-labels once, I have added them for now so that the tests don't fail.

[nicolethoen]

Event handling is not quite ideal in this example.

In other dropdown examples, if I open the menu using the keyboard, i can hit tab and it will close the menu and put focus on the next focusable element on the page (in the docs, that's usually the button)

In the other dropdown examples, I can also click outside the menu and it will close the menu.

I think it's because this new example might be missing the 'onOpenChange' prop.

[Mash707]

Yes, it was happening due to the missing onOpenChange prop. I have added it and now the menu is closing when clicking outside.