What problem does this address?

There are occasions when we would like to modify onSplit behaviour.
In the example below, we want the split Heading to be a paragraph.

We had to use patch-package to make the above change:

What is your proposed solution?

Currently, onSplit is a prop of the RichText child of BlockEdit and we don't have a way to manipulate it.

Request - allow custom onSplit, onSplitMiddle behaviour.