Added attributes, constructor, destructor, and to_string to variable …

…declaration node

include/dragon/ast/variable_declaration_node.h

@@ -4,4 +4,20 @@
 #include "../ast.h"
 
 class VariableDeclarationNode : public StatementNode {
+public:
+    Token identifier;
+    Token type;
+    std::unique_ptr<ExpressionNode> value;
+    bool is_const;
+
+    explicit VariableDeclarationNode(Token identifier, Token type, std::unique_ptr<ExpressionNode> value, bool is_const) 
+        : identifier(std::move(identifier)), type(std::move(type)), value(std::move(value)), is_const(is_const) {}
+
+    ~VariableDeclarationNode() override = default;
+
+    std::string to_string() const override {
+        return "VariableDeclarationNode(identifier: " + identifier.to_string()
+            + ", type: " + type.to_string() 
+            + ", is_const: " + (is_const ? "true" : "false") + ")";
+    }
 };