Add base commit for model extension notebooks - NER, Classify, Seq2Seq

[choudhary-shivani]

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Description: This pull request introduces three new Jupyter notebooks focused on model extension usecases, specifically for Named Entity Recognition (NER), classification, and sequence-to-sequence (Seq2Seq) models. The notebooks provide comprehensive guides on utilizing model extension within the ArcGIS Python Text API framework and Text Tools.

Notebooks Added:

1. Address Standardization Using Model Extension
   Path: guide/14-deep-learning/address_standerdization_using_model_extension.ipynb

2. Exploring Model Extensibility for Named Entity Recognition
   Path: guide/14-deep-learning/exploring_model_extensibility_for_named_entity_recognition.ipynb

3. Leveraging LLMs for Real-Time Decision Making in Calamities
   Path: guide/14-deep-learning/leveraging_llms_for_real_time_decision_making_in_calamities.ipynb