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/bloom/gaussblur.frag

@@ -0,0 +1,43 @@
+// Copyright 2020 Google LLC
+
+Texture2D textureColor : register(t1);
+SamplerState samplerColor : register(s1);
+
+cbuffer UBO : register(b0)
+{
+	float blurScale;
+	float blurStrength;
+};
+
+[[vk::constant_id(0)]] const int blurdirection = 0;
+
+float4 main([[vk::location(0)]] float2 inUV : TEXCOORD0) : SV_TARGET
+{
+	float weight[5];
+	weight[0] = 0.227027;
+	weight[1] = 0.1945946;
+	weight[2] = 0.1216216;
+	weight[3] = 0.054054;
+	weight[4] = 0.016216;
+
+	float2 textureSize;
+	textureColor.GetDimensions(textureSize.x, textureSize.y);
+	float2 tex_offset = 1.0 / textureSize * blurScale; // gets size of single texel
+	float3 result = textureColor.Sample(samplerColor, inUV).rgb * weight[0]; // current fragment's contribution
+	for(int i = 1; i < 5; ++i)
+	{
+		if (blurdirection == 1)
+		{
+			// H
+			result += textureColor.Sample(samplerColor, inUV + float2(tex_offset.x * i, 0.0)).rgb * weight[i] * blurStrength;
+			result += textureColor.Sample(samplerColor, inUV - float2(tex_offset.x * i, 0.0)).rgb * weight[i] * blurStrength;
+		}
+		else
+		{
+			// V
+			result += textureColor.Sample(samplerColor, inUV + float2(0.0, tex_offset.y * i)).rgb * weight[i] * blurStrength;
+			result += textureColor.Sample(samplerColor, inUV - float2(0.0, tex_offset.y * i)).rgb * weight[i] * blurStrength;
+		}
+	}
+	return float4(result, 1.0);
+}