zon: Add anonymous struct literal in the example

Author: perillo

lib/std/zon.zig

@@ -23,6 +23,7 @@
 //!     .b = "hello, world!",
 //!     .c = .{ true, false },
 //!     .d = .{ 1, 2, 3 },
+//!     .e = .{ .x = 13, .y = 67 },
 //! }
 //! ```
 //!