Feature: Split button

[bjarnef]

I noticed this and wonder if it would make sense to add a split button - e.g. a button as primary action + addition actions.
https://sap.github.io/ui5-webcomponents/components/SplitButton/

E.g. what used to be at "Save & Publish" + additional actions.

[bjarnef]

@iOvergaard @nielslyngsoe would something like this make sense?

I also noticed several stories for button component is broken:
https://uui.umbraco.com/?path=/story/uui-button--badge