How to edit this shader to use diffuse lighting (2D)

I found the following shader free for use which allows me to edit the hue, saturation and value of sprites in my game:

 Shader "Custom/HSVShader" {
     Properties {
         _MainTex ("Texture", 2D) = "white" {}
         _HueShift("HueShift", Float ) = 0
         _Sat("Saturation", Float) = 1
         _Val("Value", Float) = 1
     }
     SubShader {
  
         Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType" = "Transparent" }
         ZWrite Off
         Blend SrcAlpha OneMinusSrcAlpha
         Cull Off
  
         Pass
         {
             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag
             #pragma target 2.0
 
           
  
             #include "UnityCG.cginc"
  
             float3 shift_col(float3 RGB, float3 shift)
             {
             float3 RESULT = float3(RGB);
             float VSU = shift.z*shift.y*cos(shift.x*3.14159265/180);
                 float VSW = shift.z*shift.y*sin(shift.x*3.14159265/180);
                
                 RESULT.x = (.299*shift.z+.701*VSU+.168*VSW)*RGB.x
                         + (.587*shift.z-.587*VSU+.330*VSW)*RGB.y
                         + (.114*shift.z-.114*VSU-.497*VSW)*RGB.z;
                
                 RESULT.y = (.299*shift.z-.299*VSU-.328*VSW)*RGB.x
                         + (.587*shift.z+.413*VSU+.035*VSW)*RGB.y
                         + (.114*shift.z-.114*VSU+.292*VSW)*RGB.z;
                
                 RESULT.z = (.299*shift.z-.3*VSU+1.25*VSW)*RGB.x
                         + (.587*shift.z-.588*VSU-1.05*VSW)*RGB.y
                         + (.114*shift.z+.886*VSU-.203*VSW)*RGB.z;
                
             return (RESULT);
             }
  
             struct v2f {
                 float4  pos : SV_POSITION;
                 float2  uv : TEXCOORD0;
             };
  
             float4 _MainTex_ST;
  
             v2f vert (appdata_base v)
             {
                 v2f o;
                 o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
                 o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);
                 return o;
             }
 
          
  
             sampler2D _MainTex;
             float _HueShift;
             float _Sat;
             float _Val;
  
             half4 frag(v2f i) : COLOR
             {
                 half4 col = tex2D(_MainTex, i.uv);
                 float3 shift = float3(_HueShift, _Sat, _Val);
                
                 return half4( half3(shift_col(col, shift)), col.a);
             }
             ENDCG
         }
     }
     Fallback "Diffuse"
 }

My question is how to combine this with the standard 'Sprite-Diffuse' or otherwise to achieve a simple lighting effect on the sprites while retaining the ability to edit the HSV values.

I am quite new to shader programming, so please be detailed with any explanation. Thanks in advance.