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/base/textoverlay.frag

@@ -0,0 +1,10 @@
+// Copyright 2020 Google LLC
+
+Texture2D textureFont : register(t0);
+SamplerState samplerFont : register(s0);
+
+float4 main([[vk::location(0)]]float2 inUV : TEXCOORD0) : SV_TARGET
+{
+	float color = textureFont.Sample(samplerFont, inUV).r;
+	return float4(color.xxx, 1.0);
+}

data/hlsl/base/textoverlay.vert

@@ -0,0 +1,21 @@
+// Copyright 2020 Google LLC
+
+struct VSInput
+{
+	[[vk::location(0)]]float2 Pos : POSITION0;
+	[[vk::location(1)]]float2 UV : TEXCOORD0;
+};
+
+struct VSOutput
+{
+    float4 Pos : SV_POSITION;
+	[[vk::location(0)]]float2 UV : TEXCOORD0;
+};
+
+VSOutput main(VSInput input)
+{
+	VSOutput output = (VSOutput)0;
+	output.Pos = float4(input.Pos, 0.0, 1.0);
+	output.UV = input.UV;
+	return output;
+}

data/hlsl/base/uioverlay.frag

@@ -0,0 +1,15 @@
+// Copyright 2020 Google LLC
+
+Texture2D fontTexture : register(t0);
+SamplerState fontSampler : register(s0);
+
+struct VSOutput
+{
+	[[vk::location(0)]]float2 UV : TEXCOORD0;
+	[[vk::location(1)]]float4 Color : COLOR0;
+};
+
+float4 main(VSOutput input) : SV_TARGET
+{
+	return input.Color * fontTexture.Sample(fontSampler, input.UV);
+}

data/hlsl/base/uioverlay.vert

@@ -0,0 +1,33 @@
+// Copyright 2020 Google LLC
+
+struct VSInput
+{
+	[[vk::location(0)]]float2 Pos : POSITION0;
+	[[vk::location(1)]]float2 UV : TEXCOORD0;
+	[[vk::location(2)]]float4 Color : COLOR0;
+};
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+	[[vk::location(0)]]float2 UV : TEXCOORD0;
+	[[vk::location(1)]]float4 Color : COLOR0;
+};
+
+struct PushConstants
+{
+	float2 scale;
+	float2 translate;
+};
+
+[[vk::push_constant]]
+PushConstants pushConstants;
+
+VSOutput main(VSInput input)
+{
+	VSOutput output = (VSOutput)0;
+	output.Pos = float4(input.Pos * pushConstants.scale + pushConstants.translate, 0.0, 1.0);
+	output.UV = input.UV;
+	output.Color = input.Color;
+	return output;
+}