add RhaiCustomType trait and build_type method

src/lib.rs

@@ -166,7 +166,7 @@ type ExclusiveRange = std::ops::Range<INT>;
 /// An inclusive integer range.
 type InclusiveRange = std::ops::RangeInclusive<INT>;
 
-pub use api::events::VarDefInfo;
+pub use api::{build_type::RhaiCustomType, events::VarDefInfo};
 pub use ast::{FnAccess, AST};
 pub use engine::{Engine, OP_CONTAINS, OP_EQUALS};
 pub use eval::EvalContext;