请写一个Sprite2D边缘发光的shader

好的，以下是一个简单的 Unity Shader 代码实现 2D Sprite 边缘发光的效果：

Shader "Custom/SpriteOutlineGlow" {
    Properties {
        _MainTex ("Texture", 2D) = "white" {}
        _OutlineColor ("Outline Color", Color) = (1, 1, 1, 1)
        _OutlineWidth ("Outline Width", Range(0, 1)) = 0.1
    }

    SubShader {
        Tags {"Queue"="Transparent" "RenderType"="Transparent"}
        LOD 100

        Pass {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            struct appdata_t {
                float4 vertex : POSITION;
                float4 color : COLOR;
                float2 uv : TEXCOORD0;
            };

            struct v2f_t {
                float4 vertex : SV_POSITION;
                float2 uv : TEXCOORD0;
                float4 color : COLOR;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float4 _OutlineColor;
            float _OutlineWidth;

            v2f_t vert (appdata_t v) {
                v2f_t o;
                o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.color = v.color;
                return o;
            }

            fixed4 frag (v2f_t i) : SV_Target {
                fixed4 col = tex2D(_MainTex, i.uv);
                fixed4 outlineColor = _OutlineColor * col.a;

                float2 pixelSize = 1 / _ScreenParams.xy;
                float2 uv2 = i.uv + pixelSize * _OutlineWidth * 2.0;
                fixed4 col2 = tex2D(_MainTex, uv2);
                outlineColor *= (col2.a - col.a);

                col.rgb += outlineColor.rgb;
                return col;
            }
            ENDCG
        }
    }
    FallBack "Sprites/Default"
}

这个 Shader 首先通过传递的 `_MainTex` 纹理进行着色，之