README update

upgraded base image from bullseye to bookworm

upon start, kick out the existing session by clicking 'continue login…

…' when prompted, plus fixed an IB_PREFER_IBKEY parsing typo

addressed a situation where the latest version of IBG display the win…

…dow title as 'IBKR Gateway' instead of 'IB Gateway' for some accounts

IB_PREFER_IBKEY environment variable to automatically choose IB Key w…

…hen there are multiple choices of two-factor auth devices

last version without two-factor auth