Label corner without value #292
Description
Currently, Label corner props must be left or right valued. However, the right class is optional as this is the default position. It is also used in labeled inputs with a corner only class (no right).
We should relax the propTypes for the corner prop on Labels to allow boolean or left/right. This should be as easy as updating the propType, the cx helper from useValueAndKey to useKeyOrValueAndKey, and finally the common test to match.