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/ast.rs

@@ -19,6 +19,7 @@ use std::fmt::{Debug, Display};
  * assignment_statement -> IDENTIFIER "=" expression ";"
  * block_statement -> "do" statement* "end"
  * if_statement -> "if" expression "then" statement ("elif" expression "then" statement)* ("else" statement)? "end"
+ * while_statement -> "while" expression "do" statement "end"
  *
  * expression -> assignment
  * assignment -> IDENTIFIER "=" assignment | logical_or
@@ -145,6 +146,15 @@ pub enum Stmt {
         elif_branch: Vec<(Box<Expr>, Box<Stmt>)>,
         else_branch: Option<Box<Stmt>>,
     },
+    While {
+        condition: Box<Expr>,
+        body: Box<Stmt>,
+    },
+    For {
+        variable: Box<Expr>,
+        iterable: Box<Expr>,
+        body: Box<Stmt>,
+    },
 }
 
 impl Display for Stmt {
@@ -182,6 +192,12 @@ impl Display for Stmt {
                     .collect::<Vec<_>>()
                     .join("\n")
             ),
+            Stmt::While { condition, body } => todo!(),
+            Stmt::For {
+                variable,
+                iterable,
+                body,
+            } => todo!(),
         }
     }
 }
@@ -221,6 +237,12 @@ impl Debug for Stmt {
                     .collect::<Vec<_>>()
                     .join("\t\t\n")
             ),
+            Stmt::While { condition, body } => todo!(),
+            Stmt::For {
+                variable,
+                iterable,
+                body,
+            } => todo!(),
         }
     }
 }
@@ -267,6 +289,12 @@ impl AstNodeKind for Stmt {
             } => "if statement",
             Stmt::Print { expression: _ } => "print statement",
             Stmt::Stmt { expression: _ } => "statement",
+            Stmt::While { condition, body } => todo!(),
+            Stmt::For {
+                variable,
+                iterable,
+                body,
+            } => todo!(),
         }
     }
 }