Add Litematica exporter and integrate serde for serialization

- Introduced Litematica exporter with necessary data structures for Minecraft text generation.
- Added serde dependency for serialization support in multiple crates.
- Updated Cargo.toml files to include new dependencies and features.
- Created palette module for block palette management.

crates/lib/src/lib.rs

@@ -4,6 +4,7 @@ mod font;
 mod fonts;
 mod grid;
 mod models;
+mod palette;
 
 pub use engine::{GenerationOptions, TextBuilder};
 pub use error::{FontError, VoxelError};