refactor: externalize builtin forward-lit shader asset

engine/assets/builtin/shaders/forward-lit/forward-lit.vert.vk.glsl

@@ -0,0 +1,25 @@
+// XC_BUILTIN_FORWARD_LIT_VULKAN_VS
+#version 450
+layout(location = 0) in vec3 aPosition;
+layout(location = 1) in vec3 aNormal;
+layout(location = 2) in vec2 aTexCoord;
+
+layout(set = 1, binding = 0, std140) uniform PerObjectConstants {
+    mat4 gProjectionMatrix;
+    mat4 gViewMatrix;
+    mat4 gModelMatrix;
+    mat4 gNormalMatrix;
+    vec4 gMainLightDirectionAndIntensity;
+    vec4 gMainLightColorAndFlags;
+};
+
+layout(location = 0) out vec3 vNormalWS;
+layout(location = 1) out vec2 vTexCoord;
+
+void main() {
+    vec4 positionWS = gModelMatrix * vec4(aPosition, 1.0);
+    vec4 positionVS = gViewMatrix * positionWS;
+    gl_Position = gProjectionMatrix * positionVS;
+    vNormalWS = mat3(gNormalMatrix) * aNormal;
+    vTexCoord = aTexCoord;
+}