add const_assert for BitBoard

src/bitboard.rs

@@ -1,4 +1,11 @@
 use crate::board::BOARD_SIZE;
+use static_assertions::const_assert_eq;
+
+// BitBoard should be big enough to fit all points on the board
+const_assert_eq!(
+    std::mem::size_of::<BitBoard>() * 8,
+    (BOARD_SIZE * BOARD_SIZE)
+);
 
 /// 8x8
 /// TODO! look into variable length bit arrays in rust