Initialize Rust implementation of Lox interpreter

This initial commit sets up the basic structure for a Rust
implementation of the Lox interpreter, including:

- Lexer for tokenizing source code - Parser for building AST - Basic
interpreter functionality - Environment for variable storage

The core components include source tracking, error handling, and basic
expression evaluation.

example.lox

@@ -0,0 +1,19 @@
+// var Person :: struct {
+//     name: String,
+//     age: Int,
+//     address: String,
+// }
+// var func_name :: fn(param, param2) {param is Int}  do
+do
+    print "ciao";
+    1 + 2;
+    var cavallo = 1 + 2;
+    cavallo = cavallo + 1;
+    print cavallo;
+    cavallo
+end
+do
+    print "cavallo";
+    89
+end
+99