[position] Rename fields of EnPassant struct

Append _square to each one.

moves/src/en_passant.rs

@@ -5,8 +5,8 @@ use chessfriend_core::{Rank, Square};
 /// En passant information.
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub struct EnPassant {
-    target: Square,
-    capture: Square,
+    target_square: Square,
+    capture_square: Square,
 }
 
 impl EnPassant {
@@ -34,18 +34,21 @@ impl EnPassant {
     /// ```
     pub fn from_target_square(target: Square) -> Option<Self> {
         match Self::_capture_square(target) {
-            Some(capture) => Some(Self { target, capture }),
+            Some(capture) => Some(Self {
+                target_square: target,
+                capture_square: capture,
+            }),
             None => None,
         }
     }
 
     /// The square the capturing piece will move to.
     pub fn target_square(&self) -> Square {
-        self.target
+        self.target_square
     }
 
     /// The square on which the captured pawn sits.
     pub fn capture_square(&self) -> Square {
-        self.capture
+        self.capture_square
     }
 }