improve: add TerminalKeyboardEvent toString

lib/src/core/input/handler.dart

@@ -54,6 +54,11 @@ class TerminalKeyboardEvent {
       platform: platform ?? this.platform,
     );
   }
+
+  @override
+  String toString() {
+    return 'TerminalKeyboardEvent(key: $key, shift: $shift, ctrl: $ctrl, alt: $alt, state: $state, altBuffer: $altBuffer, platform: $platform)';
+  }
 }
 
 /// TerminalInputHandler contains the logic for translating a [TerminalKeyboardEvent]