Hard Light Blending mode

[trufflefluffle]

The hard light blending mode is a very useful blending mode for adding shadows and lights. It should be relatively easy to add as it is the same as Overlay BUT the A and B inputs are switched.
For example, if we do our lighting on layer A and then do colors on layer B set to Overlay, we would get the same result if layer A was our colors and layer B was our lighting set to Hardlight.

Adding the hard light blending mode would allow us to just use a lighting layer on top of our colors.