Subpixel rendering (#186)

Reviewed-on: https://git.madvoxel.net/OpenVulkano/OpenVulkano/pulls/186
Reviewed-by: Georg Hagen <georg.hagen@madvoxel.com>
Co-authored-by: ohyzha <oleksii.hyzha.ext@madvoxel.com>
Co-committed-by: ohyzha <oleksii.hyzha.ext@madvoxel.com>

openVulkanoCpp/Shader/subpixelText.frag

@@ -0,0 +1,20 @@
+#version 450
+
+layout(location = 0) in vec4 color;
+layout(location = 1) in vec4 bgColor;
+layout(location = 2) in vec2 texCoord;
+
+layout(location = 0) out vec4 outColor;
+
+layout(set = 2, binding = 0) uniform sampler2D texSampler;
+
+void main()
+{
+    vec4 sampled = texture(texSampler, texCoord);
+    float alpha = max(sampled.r, max(sampled.g, sampled.b));
+    outColor = vec4(color) * vec4(sampled.rgb, alpha);
+    if (bgColor.a != 0)
+    {
+      outColor = mix(bgColor, outColor, alpha);
+    }
+}