Add spatial edge feathering to Luminance & Color Range masks

The problem:

Lightroom Classic’s current Luminance and Color Range masks often produce harsh, unnatural transitions. Even when using the available range feathering, fine details and local contrast are still flattened or even destroyed. This happens because the existing feathering only softens the tonal selection (the range), not the spatial edges of the mask.

The solution:

Introduce a spatial edge feathering slider, similar to Photoshop’s mask feather control (see picture). This would soften the geometric edges of the mask independently of the luminance or color thresholds, so that local contrast and fine details are preserved.