Add tensorflow example for the image classification task guide
For the same dataset and steps as in https://huggingface.co/docs/transformers/tasks/image_classification, 
add sample code for the TensorFlow part. 

This example can supplement the existing guide and can be helpful to those who choose TensorFlow over PyTorch and would like to use Transformers for image classification. 
Related PR: https://github.com/huggingface/transformers/pull/21038