Update Readme.md

adjusted removed changes for function calling. used gpt4 again, did not seem to have access yet

adjusted for function calling to avoid deprecation, changed to gpt4

added chat names

added fetch chat history endpoint to api

adjusted mongodb connection

added proper error responses

added user logging

adjusted document in mongodb

added mongodb install

added endpoint to save chathistory to mongodb

adjusted system message for gpt

tryed reverting to an older verision

gpt 4

switched to gpt-3.5-turbo