added read me to app

[jonco5555]

Note

Adds initial README for the Streamlit-based MkDocs chatbot app to document setup and usage.

• New app/README.md detailing purpose, features, and requirements
• Installation instructions via uv and pip
• Configuration of Streamlit secrets: GOOGLE_API_KEY, GOOGLE_LLM_MODEL, GOOGLE_EMB_MODEL
• Run instructions (streamlit run main.py) and deployment notes for Streamlit Cloud
• High-level workflow: document loading from docs/, vector indexing with Google embeddings, chat query processing, and LLM response generation

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