Add option to use zig shaders

examples/shaders/fragment.zig

@@ -0,0 +1,13 @@
+const std = @import("std");
+const gpu = std.gpu;
+
+extern const v_color: @Vector(3, f32) addrspace(.input);
+extern var f_color: @Vector(4, f32) addrspace(.output);
+
+export fn main() callconv(.spirv_fragment) void {
+    gpu.location(&v_color, 0);
+    gpu.location(&f_color, 0);
+
+    const temp: @Vector(4, f32) = .{ v_color[0], v_color[1], v_color[2], 1.0 };
+    f_color = temp;
+}