Added AdamW from tf.keras.optimizers to external_configurables.

AdamW optimizer is supported in current version of tensorflow(https://www.tensorflow.org/api_docs/python/tf/keras/optimizers)

PiperOrigin-RevId: 636486640

Author: Gin-Config Team

gin/tf/external_configurables.py

@@ -98,6 +98,8 @@ def piecewise_constant(global_step, *args, **kwargs):
     tf.keras.optimizers.Adagrad, module='tf.keras.optimizers')
 config.external_configurable(
     tf.keras.optimizers.Adam, module='tf.keras.optimizers')
+config.external_configurable(
+    tf.keras.optimizers.AdamW, module='tf.keras.optimizers')
 config.external_configurable(
     tf.keras.optimizers.Adamax, module='tf.keras.optimizers')
 config.external_configurable(