Add magic bitboard generation

src/movegen/magic/mod.rs

@@ -14,7 +14,6 @@ pub struct Magic {
 
 impl Magic {
     /// Compute the index into the magics database for this set of `blockers`.
-    #[allow(unused)] // FIXME: remove once used
     pub fn get_index(&self, blockers: Bitboard) -> usize {
         let relevant_occupancy = (blockers & self.mask).0;
         let base_index = ((relevant_occupancy.wrapping_mul(self.magic)) >> self.shift) as usize;