重写脚本解释器的实现，提高其可读性。

Serein.Script/Node/ValueNode/BooleanNode.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Serein.Script.Node
+{
+    /// <summary>
+    /// 布尔字面量
+    /// </summary>
+    public class BooleanNode : ASTNode
+    {
+        public bool Value { get; }
+        public BooleanNode(bool value) => Value = value;
+    }
+}