Internal: b/140828801

There are many use cases when it is desired to capture the actual key being pressed in a input widget.

A classic example is a "tag input" use case. You have a list of "tags/labels/chips" that is followed by a text input. When you add some text in and submit it, a new tag/label/chip is added. When you press backspace/delete and the text input is empty, then the most recent tag/label/chip should be removed.

We will need a "onKeyPress" callback so that we can know if the backspace/delete key was being pressed.