Openai-pygenerator

Added new environment variable `GPT_REQUEST_TIMEOUT_SECONDS` which overrides the `request_timeout` parameter when calling the OpenAI API.

For more details see https://community.openai.com/t/configuring-timeout-for-chatcompletion-python/107226/24?page=2.

Added new environment variable `GPT_REQUEST_TIMEOUT_SECONDS` which overrides the `request_timeout` parameter when calling the OpenAI API.

For more details see https://community.openai.com/t/configuring-timeout-for-chatcompletion-python/107226/24?page=2.

- updated readme with explanations and links to functional-programming concepts

- retry on 500 status

- retry on openai.error.TimeoutError

- catch more general TimeoutError when retrying (includes ReadTimeoutError, ConnectTimeoutError etc.)