added 3 new notebooks provided by AR on GitHub

Neu/Cancellation/hotel_cancellation.ipynb

Neu/Cancellation/hotel_reservations.csv

Neu/Cancellation/requirements.txt

Neu/Price/ML Model_Price Prediction Retail.ipynb

Neu/Sentiment/data/cleaned_data.csv

Neu/Sentiment/data/data_lem.csv

Neu/Sentiment/data/data_stem.csv

Neu/Sentiment/data/data_swr.csv

Neu/Sentiment/data/raw_data.csv

Neu/Sentiment/notebook.ipynb

Neu/Sentiment/results.xlsx