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/ssao/blur.frag

@@ -0,0 +1,24 @@
+// Copyright 2020 Google LLC
+
+Texture2D textureSSAO : register(t0);
+SamplerState samplerSSAO : register(s0);
+
+float4 main([[vk::location(0)]] float2 inUV : TEXCOORD0) : SV_TARGET
+{
+	const int blurRange = 2;
+	int n = 0;
+	int2 texDim;
+	textureSSAO.GetDimensions(texDim.x, texDim.y);
+	float2 texelSize = 1.0 / (float2)texDim;
+	float result = 0.0;
+	for (int x = -blurRange; x < blurRange; x++)
+	{
+		for (int y = -blurRange; y < blurRange; y++)
+		{
+			float2 offset = float2(float(x), float(y)) * texelSize;
+			result += textureSSAO.Sample(samplerSSAO, inUV + offset).r;
+			n++;
+		}
+	}
+	return result / (float(n));
+}