Add slang shaders for additional samples

shaders/slang/imgui/ui.slang

@@ -0,0 +1,37 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+struct VSInput
+{
+    float2 Pos;
+    float2 UV;
+    float4 Color;
+};
+
+struct VSOutput
+{
+    float4 Pos : SV_POSITION;
+    float2 UV;
+    float4 Color;
+};
+
+Sampler2D fontSampler;
+
+[shader("vertex")]
+VSOutput vertexMain(VSInput input, uniform float2 scale, uniform float2 translate)
+{
+    VSOutput output;
+    output.UV = input.UV;
+    output.Color = input.Color;
+    output.Pos = float4(input.Pos * scale + translate, 0.0, 1.0);
+    return output;
+}
+
+[shader("fragment")]
+float4 fragmentMain(VSOutput input)
+{
+    return input.Color * fontSampler.Sample(input.UV);
+}