Removed useless index

Sources/Engine/Square.swift

@@ -33,6 +33,19 @@ public struct Square: Equatable {
 				}
 			}
 
+			public var value: Int8 {
+				return switch self {
+				case .a: 1
+				case .b: 2
+				case .c: 3
+				case .d: 4
+				case .e: 5
+				case .f: 6
+				case .g: 7
+				case .h: 8
+				}
+			}
+
 			public var description: String {
 				self.rawValue.uppercased()
 			}
@@ -60,7 +73,6 @@ public struct Square: Equatable {
 	}
 
 	public let position: Position
-	public let index: Int
 	public internal(set) var piece: Piece? = nil
 	public let color: Color