added another openai model

app.py

@@ -48,7 +48,7 @@ with st.sidebar:
     elif provider == 'mistralai':
         llm_list =[]
     elif provider == 'openai':
-        llm_list = ['gpt-3.5-turbo', 'gpt-4', 'gpt-4-turbo', 'gpt-4o']
+        llm_list = ['gpt-3.5-turbo', 'gpt-4', 'gpt-4-turbo', 'gpt-4o', 'gpt-4o-mini']
     else:
         llm_list = []