Move example-only tabled dependency to dev-dependencies

[xiaguan]

Problem

sideway 0.4.3 declares tabled = "0.18" under [dependencies], but tabled appears to be used only by the cmtime and show_gids examples.

As a result, every downstream library user pulls in this chain:

sideway 0.4.3
└── tabled 0.18.0
    └── tabled_derive 0.10.0
        └── proc-macro-error2 2.0.1

With Rust 1.97.0, Cargo reports a future-incompatibility warning from proc-macro-error2:

warning[E0365]: extern crate `proc_macro` is private and cannot be re-exported
  --> proc-macro-error2-2.0.1/src/lib.rs:494:13
   |
494 |     pub use proc_macro;
   |             ^^^^^^^^^^
   |
   = warning: this was previously accepted by the compiler but is being phased out;
     it will become a hard error in a future release

The direct upstream issue is GnomedDev/proc-macro-error-2#13.

Suggested fix

Move tabled = "0.18" from [dependencies] to [dev-dependencies]. Cargo makes dev-dependencies available to examples, so this should preserve both example binaries while removing an example-only dependency and its proc macro from downstream library builds.

Suggested validation:

cargo check --lib
cargo check --examples
cargo test

Rust compiler context: rustc 1.97.0 (2d8144b78 2026-07-07).

[dragonJACson]

Thanks for reporting, will move it to [dev-dependencies] in next version.