GUI: Box drawing

assets/shaders/includes/gui_box_common.glsl

@@ -0,0 +1,14 @@
+struct Box {
+    vec4 backgroundColor;
+    vec4 borderColor;
+    vec2 positionSSPX;
+    vec2 sizePX;
+    float borderWidthPX;
+    float borderRadiusPX;
+};
+
+#include "global_uniforms.glsl"
+
+layout(set = 0, binding = 1, scalar) readonly buffer Boxes {
+    Box _Boxes[];
+};