Can now initialize board with FEN

Sources/Engine/Pieces/Piece.swift

@@ -12,15 +12,18 @@ public enum Kind: String, CaseIterable {
 		}
 	}
 
-
 	public static subscript(_ c: Character) -> (Self, Color)? {
 		let v = c.uppercased()
 
-		guard v == "N" || (Self.allCases.contains { String($0.rawValue.first!) == v}) else {
+		guard
+			v == "N"
+				|| (Self.allCases.contains { String($0.rawValue.first!) == v })
+		else {
 			return nil
 		}
 
-		let kind: Self = switch v {
+		let kind: Self =
+			switch v {
 			case "P": .Pawn
 			case "N": .Knight
 			case "B": .Bishop
@@ -28,7 +31,7 @@ public enum Kind: String, CaseIterable {
 			case "Q": .Queen
 			case "K": .King
 			default: .Pawn
-		}
+			}
 
 		let color: Color = c.isUppercase ? .White : .Black
 
@@ -37,6 +40,7 @@ public enum Kind: String, CaseIterable {
 }
 
 public protocol Piece {
+	var board: Board? { get }
 	var color: Color { get }
 	var unicodeRepresentation: String { get }
 	var kind: Kind { get }