feat: Implement AST binder and VM

Adds a new `Binder` struct that traverses the AST and resolves variable
references to concrete `Address` types (Local, Upvalue, Global). This
information is crucial for the Virtual Machine's execution phase.

Introduces the `BoundKind` enum to represent the AST after binding.

The `VM` is updated to handle `BoundKind` nodes and execute the bound
AST.
It now manages a call stack, local variables, and closures for function
calls and upvalue capturing.

The `Environment` struct is enhanced to manage global variables and
provide
a unified interface for parsing, binding, and executing scripts. It also
includes basic standard library functions.

src/ast/mod.rs

@@ -2,8 +2,14 @@ pub mod types;
 pub mod nodes;
 pub mod lexer;
 pub mod parser;
+pub mod compiler;
+pub mod vm;
+pub mod environment;
 
 pub use types::*;
 pub use nodes::*;
 pub use lexer::*;
 pub use parser::*;
+pub use compiler::*;
+pub use vm::*;
+pub use environment::*;