[model_cards] Add model cards for Urduhack model (roberta-urdu-small) (#6536)

* [model_cards] roberta-urdu-small added.

* [model_cards] typo fixed.

* Tweak license format (yaml expects a simple string)

Co-authored-by: Ikram Ali <mrikram1989>
Co-authored-by: Julien Chaumond <chaumond@gmail.com>

model_cards/urduhack/roberta-urdu-small/README.md

+---
+language: ur
+thumbnail: https://raw.githubusercontent.com/urduhack/urduhack/master/docs/_static/urduhack.png
+tags:
+- roberta-urdu-small
+- urdu
+- transformers
+license: mit
+---
+## roberta-urdu-small
+
+[![License: MIT](https://img.shields.io/badge/license-MIT-blue.svg)](https://github.com/urduhack/urduhack/blob/master/LICENSE)
+### Overview
+**Language model:** roberta-urdu-small
+**Model size:** 125M
+**Language:** Urdu
+**Training data:** News data from urdu news resources in Pakistan
+### About roberta-urdu-small
+roberta-urdu-small is a language model for urdu language.
+```
+from transformers import pipeline
+fill_mask = pipeline("fill-mask", model="urduhack/roberta-urdu-small", tokenizer="urduhack/roberta-urdu-small")
+```
+## Training procedure
+roberta-urdu-small was trained on urdu news corpus. Training data was normalized using normalization module from
+urduhack to eliminate characters from other languages like arabic.
+
+### About Urduhack
+Urduhack is a Natural Language Processing (NLP) library for urdu language.
+Github: https://github.com/urduhack/urduhack