chore: make bitboard internals pub again :(

where my const traits at rust

ataxx/src/bitboard.rs

@@ -44,7 +44,7 @@ use crate::{File, Rank, Square};
 /// assert_eq!(!x, BitBoard::UNIVERSE - x); // Complement
 /// ```
 #[derive(Copy, Clone, PartialEq, Eq, FromPrimitive)]
-pub struct BitBoard(u64);
+pub struct BitBoard(pub u64);
 
 /// bitboard is a macro which allows creation of BitBoard values from their
 /// graphical representation with (.)s and (X)s inside the macro call.