Add ar rest reviews
Copy-pasted from the Slack discussion:
the annotation and language creators should be found , not unknown
the example should go under the "Data Instances" paragraph, not "Data fields"
can you remove the abstract from the citation and add it to the dataset description? More people will see that @yjernite done! thanks for the feedback @lhoestq not sure why it's failing tests now, I only changed cosmetics You can ignores these errors
```

=========================== short test summary info ===========================
FAILED tests/test_dataset_common.py::LocalDatasetTest::test_load_dataset_ajgt_twitter_ar
FAILED tests/test_dataset_common.py::LocalDatasetTest::test_load_dataset_chr_en
FAILED tests/test_dataset_common.py::RemoteDatasetTest::test_load_dataset_ajgt_twitter_ar
FAILED tests/test_dataset_common.py::RemoteDatasetTest::test_load_dataset_chr_en
FAILED tests/test_dataset_common.py::RemoteDatasetTest::test_load_dataset_great_code
```

they're fixed on master Feel free to ping me for the final review once you managed to change to ClassLabel :)  Hey @lhoestq I was able to fix it !! I think the same errors appeared on circleCI and now it's hopefully ready to be merged? @lhoestq done! thanks for your review  merging since the CI is fixed on master
added restaurants reviews in Arabic for sentiment analysis tasks