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/inputattachments/attachmentread.vert

@@ -0,0 +1,6 @@
+// Copyright 2020 Google LLC
+
+float4 main(uint VertexIndex : SV_VertexID) : SV_POSITION
+{
+	return float4(float2((VertexIndex << 1) & 2, VertexIndex & 2) * 2.0f - 1.0f, 0.0f, 1.0f);
+}