docs(README): add vectorizer in features

Author: sanjayaksaxena

README.md

@@ -14,15 +14,26 @@ winkNLP is a JavaScript library for Natural Language Processing (NLP). Designed
 It packs a rich feature set into a small foot print codebase of [under 1500 lines](https://coveralls.io/github/winkjs/wink-nlp?branch=master):
 
 1. Lossless & multilingual tokenizer
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 2. Developer friendly and intuitive API
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 3. Built-in API to aid text visualization
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 4. Easy information extraction from raw text
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 5. Extensive text pre-processing features
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 6. Pre-trained models with sizes starting from <3MB onwards
-7. Word vector integration
-8. Comprehensive NLP pipeline covering tokenization, sentence boundary detection, negation handling, sentiment analysis, part-of-speech (pos) tagging, named entity extraction, custom entities detection and pattern matching
-9. No external dependencies.
-10. Runs on web browsers
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+7. BM25-based vectorizer
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+8. Word vector integration
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+9. Comprehensive NLP pipeline covering tokenization, sentence boundary detection, negation handling, sentiment analysis, part-of-speech (pos) tagging, named entity extraction, custom entities detection and pattern matching
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+10. No external dependencies.
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+11. Runs on web browsers
 
 
 ## Installation