Add while loop support and token pretty printing

The commit adds while loop statements and improves token display
formatting:

- Implements while loop syntax and evaluation - Adds a new token pretty
printing module with configurable formatting - Improves token display
with colors and different output modes

src/frontend/parser.rs

@@ -81,6 +81,10 @@ impl Parser {
                 self.if_statement()?,
                 self.peek().source_slice.clone(),
             )),
+            (TokenType::While, _) => Ok(AstNode::new(
+                self.while_statement()?,
+                self.peek().source_slice.clone(),
+            )),
             _ => Ok(AstNode::new(
                 self.expression_statement()?,
                 self.peek().source_slice.clone(),
@@ -88,6 +92,16 @@ impl Parser {
         }
     }
 
+    fn while_statement(&mut self) -> LoxResult<Stmt> {
+        self.advance();
+        let condition = self.expression()?;
+        let body = self.block_statement()?;
+        Ok(Stmt::While {
+            condition: Box::new(condition),
+            body: Box::new(body),
+        })
+    }
+
     fn if_statement(&mut self) -> LoxResult<Stmt> {
         self.advance();
         let condition = self.expression()?;