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

example.lox

@@ -14,6 +14,10 @@ do
 end
 do
     print "cavallo";
+    while cavallo < 10 do
+        print "loop: " + cavallo;
+        cavallo = cavallo + 1;
+    end
     89
 end
 99