dillon1000/react

Add focus helper to range test, update button styles (#11134)

When testing range input change events, clicking the knob would cause
it to move if the click region wasn't precisely on the center of the
knob.

This is annoying! This commit adds a button to focus the range input
knob and takes a small pass at styling buttons.

A label would work here too, however it does not generate a focus ring
in all browsers.