For needs of our upcoming game The Legend Of The Spirit Bird I need to develop a few custom shaders. So about week ago I started with learning of shader programming in unity. So here is source code of my first custom shader for hard light blend mode like in Photoshop. So I hope it helps to someone else.
For comparison here is output of my unity shader (on the left image) and hard light blend mode in Photoshop (on the right image) .