refactor: externalize builtin forward-lit shader asset

engine/assets/builtin/shaders/forward-lit/forward-lit.vs.hlsl

@@ -0,0 +1,38 @@
+// XC_BUILTIN_FORWARD_LIT_D3D12_VS
+Texture2D gBaseColorTexture : register(t1);
+SamplerState gLinearSampler : register(s1);
+
+cbuffer PerObjectConstants : register(b1) {
+    float4x4 gProjectionMatrix;
+    float4x4 gViewMatrix;
+    float4x4 gModelMatrix;
+    float4x4 gNormalMatrix;
+    float4 gMainLightDirectionAndIntensity;
+    float4 gMainLightColorAndFlags;
+};
+
+cbuffer MaterialConstants : register(b2) {
+    float4 gBaseColorFactor;
+};
+
+struct VSInput {
+    float3 position : POSITION;
+    float3 normal : NORMAL;
+    float2 texcoord : TEXCOORD0;
+};
+
+struct PSInput {
+    float4 position : SV_POSITION;
+    float3 normalWS : TEXCOORD0;
+    float2 texcoord : TEXCOORD1;
+};
+
+PSInput MainVS(VSInput input) {
+    PSInput output;
+    float4 positionWS = mul(gModelMatrix, float4(input.position, 1.0f));
+    float4 positionVS = mul(gViewMatrix, positionWS);
+    output.position = mul(gProjectionMatrix, positionVS);
+    output.normalWS = mul((float3x3)gNormalMatrix, input.normal);
+    output.texcoord = input.texcoord;
+    return output;
+}