feat: SplitButton component

[silviuaavram]

Main action should be executed by onMainButtonClick. (should be named onButtonClick?)

Other actions should be executed by onMenuItemClick. Or by having onClick on each Menu Item.

Shorthands for both button and toggleButton.

Added open by ArrowDown+Alt and close by ArrowUp+Alt.

ToDo as future task:

• create small variation.
• CSS according to the specs.

[jurokapsiar]

does this mean people can use onClick and it will be invoked for both click on the button as well as click on the toggle?

[layershifter]

Yep, for the whole container actually. And I can't obviously what is expected

[jurokapsiar]

I vote for sending this.props back to the user. popup here is internal, no need to expose it. what do you think @layershifter?

[jurokapsiar]

actually, similarly to what we have in popup:

{ ...this.props, ...{ open: false }

[jurokapsiar]

{ ...this.props, ...{ open: popupProps.open }

[layershifter]

Please move it upper, Features section has been already created

[layershifter]

Suggested change

	export default SplitButtonExampleIconShorthand
	export default SplitButtonIconAndContentExampleShorthand

Oops, filename is not match

[layershifter]

I understand that items are not required for this example, but can we add them?

  <SplitButton
    disabled
    menu={[
      { key: 'group', content: 'New group message' },
      { key: 'channel', content: 'New channel message' },
    ]}
    button="New conversation"
  />

[layershifter]

Suggested change

	description="A split button can have its main option changed based on last selection."
	description="A SplitButton can have its main option changed based on last selection."

nit: to be consistent between sections

[layershifter]

Suggested change

	onOpenChange?: ComponentEventHandler<PopupProps>
	onOpenChange?: ComponentEventHandler<SplitButtonProps>

As I see in latest change it should be SplitButtonProps

[layershifter]

This thing is typed now

Suggested change

	static create: Function
	static create: ShorthandFactory<SplitButton>

[layershifter]

Suggested change

	_.invoke(this.props, 'onOpenChange', e, { open: false, ...this.props })
	_.invoke(this.props, 'onOpenChange', e, { ...this.props, open: false })

Order should be change otherwise a value from props will win

[layershifter]

Suggested change

	_.invoke(this.props, 'onOpenChange', e, { open: popupProps.open, ...this.props })
	_.invoke(this.props, 'onOpenChange', e, { ...this.props, open: popupProps.open })

[layershifter]

Yep, for the whole container actually. And I can't obviously what is expected

[layershifter]

Suggested change

	_.invoke(this.props, 'onOpenChange', e, { open, ...this.props })
	_.invoke(this.props, 'onOpenChange', e, { ...this.props, open })