Add Adan to __init__.py

Author: twmht

timm/optim/__init__.py

@@ -3,6 +3,7 @@
 from .adahessian import Adahessian
 from .adamp import AdamP
 from .adamw import AdamW
+from .adan import Adan
 from .lamb import Lamb
 from .lars import Lars
 from .lookahead import Lookahead