Lib: Implement split button

[xak]

Detailed description

Split action

The button consists of one or two clickable areas. The first area can either contain text or any kind of content. The second area (optional) contains a drop-down arrow.

Note: This should only be available for --emphasized buttons.

Reference

Example at https://www.w3schools.com/howto/howto_css_button_split.asp

Design at https://app.zeplin.io/project/5a8c458b6e231fc65bddbdfb/dashboard?seid=5b314acf0473da4f36a101fa

[xak]

@LeoT7508 Can you prioritize design specs for the split button and show amnestying example with icon on the right?

[LeoT7508]

@xak

Yes, this is already done. Design sheets will be uploaded this week.

[LeoT7508]

@xak

Button design sheet attached.