Support in auto close/auto open to min/max size

[Michael101sh]

Hello, I want to add a button for auto close/auto open to min/max size. Please add an API for:

1. Adding a button (icon) on the top of the splitter line. In this case for auto close/auto open to min/max size. Using the renderSplitter prop - prevents calling the onClick handler of the added button.
2. Logic of setting actual size internally, for supporting the above feature.

Regards, Michael