create readme for spentaur/yelp model (#3874)

* create readme for spentaur/yelp model

* update spentaur/yelp/README.md

* remove typo

model_cards/spentaur/yelp/README.md

+# DistilBERT Yelp Review Sentiment
+This model is used for sentiment analysis on english yelp reviews.  
+It is a DistilBERT model trained on 1 million reviews from the yelp open dataset.  
+It is a regression model, with outputs in the range of ~-2 to ~2. With -2 being 1 star and 2 being 5 stars.  
+It was trained using the [ktrain](https://github.com/amaiya/ktrain) because of it's ease of use.
+
+Example use:
+
+```
+tokenizer = AutoTokenizer.from_pretrained(
+    'distilbert-base-uncased', use_fast=True)
+model = TFAutoModelForSequenceClassification.from_pretrained(
+    "spentaur/yelp")
+    
+review = "This place is great!"
+input_ids = tokenizer.encode(review, return_tensors='tf')
+pred = model(input_ids)[0][0][0].numpy()
+# pred should === 1.9562385
+```