feat: add docstring to EndpointHandler.__call__ ; when multiple inputs are sent, the output now also contains a token_list k/v pair for easier human inspection
chore: split the dependencies over two files: requirements.txt (used by HF Inference Endpoint) and requirements_extra.txt (only for local development) . Goal is to prevent the error 'Cannot uninstall 'blinker' seen in the HF Inference Endpoint logs
