feat: Implement compiler and virtual machine for Fig language

- Added Compiler class with methods for compiling programs, statements, and expressions.
- Introduced Proto structure to hold compiled bytecode and constants.
- Implemented expression compilation including literals, identifiers, and infix expressions.
- Developed statement compilation for variable declarations and expression statements.
- Created a VM class to execute compiled bytecode with support for arithmetic and comparison operations.
- Added Object and Value classes for handling different data types and memory management.
- Implemented String and Struct objects for enhanced data representation.
- Established a parser for parsing variable declarations and statements.
- Included tests for the VM and object representations.

src/Ast/Stmt/ExprStmt.hpp

@@ -0,0 +1,35 @@
+/*!
+    @file src/Ast/Stmt/ExprStmt.hpp
+    @brief ExprStmt定义
+    @author PuqiAR (im@puqiar.top)
+    @date 2026-02-19
+*/
+
+#pragma once
+
+#include <Ast/Base.hpp>
+
+namespace Fig
+{
+    struct ExprStmt final : public Stmt
+    {
+        Expr *expr;
+
+        ExprStmt()
+        {
+            type = AstType::ExprStmt;
+        }
+
+        ExprStmt(Expr *_expr) :
+            expr(_expr)
+        {
+            type = AstType::ExprStmt;
+            location = _expr->location;
+        }
+
+        virtual String toString() const override
+        {
+            return std::format("<ExprStmt: {}>", expr->toString());
+        }
+    };
+}