NER Demo

**Is your feature request related to a problem? Please describe.**
Implement a demo for NER with Streamlit.

**Reference**
* [An example](https://demo.johnsnowlabs.com/healthcare/NER_CLINICAL/)
* [A tutorial](https://nlu.johnsnowlabs.com/docs/en/streamlit_viz_examples)
* [spacy-streamlit](https://spacy.io/universe/project/spacy-streamlit)

Start by reviewing the linked John Snow Labs NER demo, Streamlit visualization tutorial, and spacy-streamlit example to determine the expected interaction and presentation. Compare those references with the repository structure, then confirm that a Streamlit NER demo runs and provides the intended clinical-entity visualization.

Written by the indexing model from the issue text.