added TTC4900: A Benchmark Data for Turkish Text Categorization dataset
@lhoestq, can you help with creating dummy_data?
 Hi @yavuzKomecoglu did you manage to build the dummy data ? > Hi @yavuzKomecoglu did you manage to build the dummy data ?

Hi, sorry for the return. I've created dummy_data.zip manually. > Nice thank you !
> 
> Before we merge can you fill the two sections of the dataset card I suggested ?
> And also remove one remaining print statement

I updated your suggestions. Thank you very much for your support. I think you accidentally pushed the readme of another dataset (name_to_nation).
I removed it so you have to `git pull`

Because of that I guess your changes about the ttc4900 was not included.
Feel free to ping me once they're added


 > I think you accidentally pushed the readme of another dataset (name_to_nation).
> I removed it so you have to `git pull`
> 
> Because of that I guess your changes about the ttc4900 was not included.
> Feel free to ping me once they're added

I did `git pull` and updated readme **ttc4900**. merging since the Ci is fixed on master
This PR adds the TTC4900 dataset which is a Turkish Text Categorization dataset by me and @basakbuluz. 

Homepage: [https://www.kaggle.com/savasy/ttc4900](https://www.kaggle.com/savasy/ttc4900)
Point of Contact: [Savaş Yıldırım](mailto:savasy@gmail.com) / @savasy
