Add slang shaders for shader objects sample

shaders/slang/shaderobjects/phong.slang

@@ -0,0 +1,65 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+struct VSInput
+{
+    float3 Pos;
+    float3 Normal;
+    float3 Color;
+};
+
+struct VSOutput
+{
+    float4 Pos : SV_POSITION;
+    float3 Normal;
+    float3 Color;
+    float3 ViewVec;
+    float3 LightVec;
+};
+
+struct UBO
+{
+    float4x4 projection;
+    float4x4 model;
+    float4 lightPos;
+};
+ConstantBuffer<UBO> ubo;
+
+Sampler2D samplerColor;
+
+[shader("vertex")]
+VSOutput vertexMain(VSInput input)
+{
+    VSOutput output;
+    output.Color = input.Color;
+    output.Pos = mul(ubo.projection, mul(ubo.model, float4(input.Pos.xyz, 1.0)));
+
+    float4 pos = mul(ubo.model, float4(input.Pos, 1.0));
+    output.Normal = mul((float4x3)ubo.model, input.Normal).xyz;
+    float3 lPos = mul((float4x3)ubo.model, ubo.lightPos.xyz).xyz;
+    output.LightVec = lPos.xyz - pos.xyz;
+    output.ViewVec = -pos.xyz;
+
+    return output;
+}
+
+[shader("fragment")]
+float4 fragmentMain(VSOutput input)
+{
+    // Desaturate color
+    float3 color = float3(lerp(input.Color, float3(dot(float3(0.2126, 0.7152, 0.0722), input.Color)), 0.65));
+
+    // High ambient colors because mesh materials are pretty dark
+    float3 ambient = color;
+
+	float3 N = normalize(input.Normal);
+    float3 L = normalize(input.LightVec);
+    float3 V = normalize(input.ViewVec);
+    float3 R = reflect(-L, N);
+    float3 diffuse = max(dot(N, L), 0.0) * color;
+    float3 specular = pow(max(dot(R, V), 0.0), 32.0) * float3(0.35);
+    return float4(ambient + diffuse * 1.75 + specular, 1.0);
+}