move unity package to the root

Documentation~/README.md

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+# Mixbox for Unity
+
+Open `Window` > `Package Manager` and choose ` + ` > `Add packge from git URL...`:
+```
+https://github.com/scrtwpns/mixbox.git#upm
+```
+
+## Script
+```csharp
+using UnityEngine;
+using Scrtwpns.Mixbox;
+
+public class NewBehaviourScript : MonoBehaviour
+{
+    void Start()
+    {
+        Color color1 = new Color(0.0f, 0.129f, 0.522f); // blue
+        Color color2 = new Color(0.988f, 0.827f, 0.0f); // yellow
+        float t = 0.5f;                                 // mixing ratio
+
+        Color colorMix = Mixbox.Lerp(color1, color2, t);
+
+        Debug.Log(colorMix);
+    }
+}
+```
+```csharp
+Color MixThree(Color color1, Color color2, Color color3)
+{
+    MixboxLatent z1 = Mixbox.RGBToLatent(color1);
+    MixboxLatent z2 = Mixbox.RGBToLatent(color2);
+    MixboxLatent z3 = Mixbox.RGBToLatent(color3);
+
+    // mix 30% of color1, 60% of color2, and 10% of color3
+    MixboxLatent zMix = 0.3f*z1 + 0.6f*z2 + 0.1f*z3;
+
+    Color colorMix = Mixbox.LatentToRGB(zMix);
+
+    return colorMix;
+}
+```
+
+## Shader
+```ShaderLab
+Shader "MixboxHelloShader"
+{
+    Properties
+    {
+        [NoScaleOffset] _MixboxLUT ("Mixbox LUT", 2D) = "white" {} // assign "Packages/Mixbox/Textures/MixboxLUT.png"
+
+        _Color1 ("Color 1", Color) = (0, 0.129, 0.522, 1) // blue
+        _Color2 ("Color 2", Color) = (0.988, 0.827, 0, 1) // yellow
+    }
+    SubShader
+    {
+        Pass
+        {
+            CGPROGRAM
+            #pragma vertex vert
+            #pragma fragment frag
+
+            #include "UnityCG.cginc"
+
+            sampler2D _MixboxLUT;
+            #include "Packages/com.scrtwpns.mixbox/ShaderLibrary/Mixbox.cginc"
+
+            fixed4 _Color1;
+            fixed4 _Color2;
+
+            struct appdata { float4 vertex : POSITION; float2 uv : TEXCOORD0; };
+            struct v2f { float2 uv : TEXCOORD0; float4 vertex : SV_POSITION; };
+
+            v2f vert (appdata v)
+            {
+                v2f o;
+                o.vertex = UnityObjectToClipPos(v.vertex);
+                o.uv = v.uv;
+                return o;
+            }
+
+            fixed4 frag (v2f i) : SV_Target
+            {
+                return MixboxLerp(_Color1, _Color2, i.uv.x);
+            }
+            ENDCG
+        }
+    }
+}
+```
+```hlsl
+float3 MixThree(float3 rgb1, float3 rgb2, float3 rgb3)
+{
+    MixboxLatent z1 = MixboxRGBToLatent(rgb1);
+    MixboxLatent z2 = MixboxRGBToLatent(rgb2);
+    MixboxLatent z3 = MixboxRGBToLatent(rgb3);
+
+    // mix together 30% of rgb1, 60% of rgb2, and 10% of rgb3
+    MixboxLatent zMix = 0.3*z1 + 0.6*z2 + 0.1*z3;
+
+    float3 rgbMix = MixboxLatentToRGB(zMix);
+
+    return rgbMix;
+}
+```
+<p align="center">
+  <img src="https://scrtwpns.com/mixbox/unity/mixboxlut-howto.png"/>
+</p>
+
+## URP Shader
+```ShaderLab
+Shader "Mixbox/Mixbox URP Sample Shader"
+{
+    Properties
+    {
+        [NoScaleOffset] _MixboxLUT ("Mixbox LUT", 2D) = "white" {} // assign "Packages/Mixbox/Textures/MixboxLUT.png"
+
+        _Color1 ("Color 1", Color) = (0, 0.129, 0.522, 1) // blue
+        _Color2 ("Color 2", Color) = (0.988, 0.827, 0, 1) // yellow
+    }
+
+    SubShader
+    {
+        Tags { "RenderType" = "Opaque" "RenderPipeline" = "UniversalRenderPipeline" }
+
+        Pass
+        {
+            HLSLPROGRAM
+            #pragma vertex vert
+            #pragma fragment frag
+
+            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
+
+            TEXTURE2D(_MixboxLUT);
+            SAMPLER(sampler_MixboxLUT);
+
+            #include "Packages/com.scrtwpns.mixbox/ShaderLibrary/Mixbox.hlsl"
+
+            struct Attributes { float4 positionOS : POSITION; float2 uv : TEXCOORD0; };
+            struct Varyings { float4 positionHCS : SV_POSITION; float2 uv : TEXCOORD0; };
+
+            CBUFFER_START(UnityPerMaterial)
+                half4 _Color1;
+                half4 _Color2;
+            CBUFFER_END
+
+            Varyings vert(Attributes IN)
+            {
+                Varyings OUT;
+                OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);
+                OUT.uv = IN.uv;
+                return OUT;
+            }
+
+            half4 frag(Varyings IN) : SV_Target
+            {
+                return MixboxLerp(_Color1, _Color2, IN.uv.x);
+            }
+            ENDHLSL
+        }
+    }
+}
+```
+
+## Shader Graph
+<p align="center">
+  <img src="https://scrtwpns.com/mixbox/unity/shadergraph_.png"/>
+</p>