feat: Implement hillshade layer

Assets/Shaders/Multiply.shader

@@ -0,0 +1,54 @@
+Shader "Map/Multiply" {
+	Properties {
+		_Color ("Color", Color) = (1, 1, 1, 1)
+		_MainTex ("Texture", 2D) = "white" { }
+	}
+	SubShader {
+		Tags {
+			"RenderType" = "Transparent"
+			"Queue" = "Transparent"
+		}
+		LOD 100
+		
+		Blend Zero SrcColor
+
+		Pass {
+			CGPROGRAM
+			#pragma vertex vert
+			#pragma fragment frag
+
+			#include "UnityCG.cginc"
+
+			struct appdata {
+				float4 vertex : POSITION;
+				float2 uv : TEXCOORD0;
+				fixed4 color : COLOR0;
+			};
+
+			struct v2f {
+				float2 uv : TEXCOORD0;
+				float4 vertex : SV_POSITION;
+				fixed4 color : COLOR0;
+			};
+
+			sampler2D _MainTex;
+			float4 _MainTex_ST;
+			fixed4 _Color;
+
+			v2f vert (appdata v) {
+				v2f o;
+				o.vertex = UnityObjectToClipPos(v.vertex);
+				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
+				o.color = v.color;
+				return o;
+			}
+
+			fixed4 frag (v2f i) : SV_Target {
+				float a = i.color.a * _Color.a;
+				fixed4 col = 1 - a * (1 - tex2D(_MainTex, i.uv) * i.color * _Color);
+				return col;
+			}
+			ENDCG
+		}
+	}
+}