Added rgb function

lib/minifb/src/minifb.zig

@@ -5,6 +5,10 @@ const minifb_c = @cImport({
 });
 const testing = std.testing;
 
+pub fn rgb(r: u8, g: u8, b: u8) u32 {
+    return @intCast(u32, r) << 16 | @intCast(u32, g) << 8 | b;
+}
+
 pub const Window = struct{
     cwin: *minifb_c.mfb_window,
 
@@ -41,5 +45,5 @@ pub const Window = struct{
         }
     }
 
-    
+
 };