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/Compiler/Compiler.cpp

@@ -0,0 +1,28 @@
+/*!
+    @file src/Compiler/Compiler.cpp
+    @brief 编译器实现
+    @author PuqiAR (im@puqiar.top)
+    @date 2026-02-18
+*/
+
+#include <Compiler/Compiler.hpp>
+
+namespace Fig
+{
+    Result<Proto *, Error> Compiler::Compile(Program *program)
+    {
+        current->proto   = new Proto();
+        current->freeReg = 0;
+
+        for (Stmt *stmt : program->nodes)
+        {
+            const auto &result = CompileStmt(static_cast<Stmt *>(stmt));
+            if (!result)
+            {
+                return std::unexpected(result.error());
+            }
+        }
+        Emit(Op::iABC(OpCode::Exit, 0, 0, 0)); // 一定要退出,这是虚拟机退出信号,否则ub
+        return current->proto;
+    }
+}; // namespace Fig