Add: TensorFlow example for semantic segmentation task guide
This PR adds a TensorFlow example to the existing [Semantic Segmentation task guide](https://huggingface.co/docs/transformers/main/en/tasks/semantic_segmentation) using the same dataset and fine-tuning steps. 

This example supplements the existing guide and can be helpful to those who choose TensorFlow over PyTorch and would like to use Transformers for semantic segmentation.
_The documentation is not available anymore as the PR was closed or merged._