Pycognaize

- Enforce utf-8 encoding when reading document.json locally

- Add Document.to_pdf() feature
- Add annotate_pdf() function in document.py
- Add Unittests for Document.to_pdf()
- Fix requirement (fitz to pymupdf)

- Make evaluate method of Model class abstract

- Add handling repeating field and group cases in evaluate functionality of model

- Rename Model.predict_based_on abstract method to `Model.copy` method
- Remove predict_based_on method from test_model ExampleModel class

- Add Model.execute_based_on_match, Model.predict_based_on, and Model._post_response methods
- Add separate `Index._store` method
- Add `response_to_dict` method to index class for transformation of the response to needed format - {doc_id: encoding}
- Update `execute_based_on_match` method in model class to get document object for matched base document"
- Remove INDEX from Model
- Change Index to create fields for matched document ID and confidence