Add chess_events.dart file.

lib/chess_bloc/chess_events.dart

@@ -0,0 +1,18 @@
+import 'package:mchess/chessapp/chess_utils.dart';
+
+abstract class ChessEvent {}
+
+class PieceMoved extends ChessEvent {
+  final ChessCoordinate startSquare;
+  final ChessCoordinate endSquare;
+
+  PieceMoved({required this.startSquare, required this.endSquare});
+}
+
+class PreCheckMove extends ChessEvent {
+  final ChessMove move;
+
+  PreCheckMove({required this.move});
+}
+
+class BoardFlippedEvent extends ChessEvent {}