WIP: D3D11VA support

Overlays work, but drawing the actual video is unimplemented

app/shaders/d3d11_vertex.hlsl

@@ -0,0 +1,19 @@
+struct ShaderInput
+{
+    float2 pos : POSITION;
+    float2 tex : TEXCOORD0;
+};
+
+struct ShaderOutput
+{
+    float4 pos : SV_POSITION;
+    float2 tex : TEXCOORD0;
+};
+
+ShaderOutput main(ShaderInput input) 
+{
+    ShaderOutput output;
+    output.pos = float4(input.pos, 0.0f, 1.0f);
+    output.tex = input.tex;
+    return output;
+}