vulkan: add support for blend buffers

src/gfx_apis/vulkan/shaders/transfer_functions.glsl

@@ -0,0 +1,21 @@
+#ifndef TRANSFER_FUNCTIONS_GLSL
+#define TRANSFER_FUNCTIONS_GLSL
+
+vec3 eotf_srgb(vec3 c) {
+    return mix(
+        c * vec3(1.0 / 12.92),
+        pow((c + vec3(0.055)) / vec3(1.055), vec3(2.4)),
+        greaterThan(c, vec3(0.04045))
+    );
+}
+
+vec3 oetf_srgb(vec3 c) {
+    c = clamp(c, 0.0, 1.0);
+    return mix(
+        c * vec3(12.92),
+        vec3(1.055) * pow(c, vec3(1/2.4)) - vec3(0.055),
+        greaterThan(c, vec3(0.0031308))
+    );
+}
+
+#endif