Swap file and rank in Position

Because the chess positions read as "file-rank"

rs/src/ui.rs

@@ -103,7 +103,7 @@ impl board::Position {
         let file = board::File::parse(chars.next().ok_or(())?)?;
         let rank = board::Rank::parse(chars.next().ok_or(())?)?;
         if chars.next().is_none() {
-            Ok(board::Position::new(rank, file))
+            Ok(board::Position::new(file, rank))
         } else {
             Err(())
         }