Add shaders re-implemented in HLSL

These were written against the shaders at revision eddd724e7.
There have been changes made since then, which will need to be mirrored.

See `data/hlsl/README.md` for the current status of each sample.

data/hlsl/computecloth/cloth.frag

@@ -0,0 +1,24 @@
+// Copyright 2020 Google LLC
+
+Texture2D textureColor : register(t1);
+SamplerState samplerColor : register(s1);
+
+struct VSOutput
+{
+[[vk::location(0)]]float2 UV : TEXCOORD0;
+[[vk::location(1)]]float3 Normal : NORMAL0;
+[[vk::location(2)]]float3 ViewVec : TEXCOORD1;
+[[vk::location(3)]]float3 LightVec : TEXCOORD2;
+};
+
+float4 main (VSOutput input) : SV_TARGET
+{
+	float3 color = textureColor.Sample(samplerColor, input.UV).rgb;
+	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), 0.15) * float3(1, 1, 1);
+	float3 specular = pow(max(dot(R, V), 0.0), 8.0) * float3(0.2, 0.2, 0.2);
+	return float4(diffuse * color.rgb + specular, 1.0);
+}