feat(typedef): re-export build_validator from validation module

Re-export validation::build_validator at the crate root so consumers can
call alknet_typedef::build_validator(schema) directly. The data_access
functions remain module-qualified (alknet_typedef::data_access::read_u32)
since there are 28 of them and re-exporting all would be noisy.

crates/alknet-typedef/src/lib.rs

@@ -35,4 +35,5 @@ pub use error::TypedefError;
 pub use schema::{
     parse_align, parse_discriminator, parse_encoding, parse_endian, parse_max_length,
     normalize_refs, DiscriminatorKind, Endian, VariableEncoding,
-};
+};
+pub use validation::build_validator;