RGB shift alias

BUR #20659 has been rejected.

create alias rgb_shift -> chromatic_aberration

Utility alias for findability. Another commonly-known term.
Fine.

When I think "RGB Shift" I am thinking more the lines of shifting the hue of an image in some image editing software, not so much that optical distortion effect.

The bulk update request #20659 (forum #257712) has been rejected by @World_Funeral.