Added MistralAI code and customized LangChain Programming For Beginners scripts from Nathan Sebhastian.

Before running the scripts, install the required dependencies using pip as shown below:

pip install -r requirements.txt

Once the dependencies are installed, rename .env.sample to .env and fill in the required API keys in the file.

Then, you can try running one of the scripts with python as follows:

python 02_Simple_Q\&A_Gemini/app_gemini.py 

Starting from Chapter 5, use streamlit to run the application:

streamlit run 05_Adding_Streamlit_GUI/app_gpt.py