Add news_sentiment.parquet and README.md

README.md

@@ -13,7 +13,7 @@ description: >-
 
 ```python
 from datasets import load_dataset
-df_news_sentiment = load_dataset("sovai/news_sentiment", split="train").to_pandas().set_index(["article_id","date"])
+df_news_sentiment = load_dataset("sovai/news_sentiment", split="train").to_pandas().set_index(["ticker","date"])
 ```