Add slang shaders for additional samples

shaders/slang/textoverlay/text.slang

@@ -0,0 +1,35 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+ struct VSInput
+{
+    float2 Pos;
+    float2 UV;
+};
+
+struct VSOutput
+{
+    float4 Pos : SV_POSITION;
+    float2 UV;
+};
+
+Sampler2D samplerFont;
+
+[shader("vertex")]
+VSOutput vertexMain(VSInput input)
+{
+    VSOutput output;
+    output.Pos = float4(input.Pos, 0.0, 1.0);
+    output.UV = input.UV;
+    return output;
+}
+
+[shader("fragment")]
+float4 fragmentMain(VSOutput input)
+{
+	float color = samplerFont.Sample(input.UV).r;
+	return color.xxxx;
+}