Add `--log-dir` option to the CLI

[andersy005]

Currently, if neither of $TMPDIR and $HOME environment variables are defined on the remote machine, we terminate the connection and exit. We should allow users to override this behavior via a --log-dir option.

jupyter-forward/jupyter_forward/core.py

Lines 249 to 254 in 917c142

	tmp_dir_error_message = '$TMPDIR is not defined'
	home_dir_error_message = '$HOME is not defined'
	console.print(
	f'[bold red]Can not determine directory for log file:\n{home_dir_error_message}\n{tmp_dir_error_message}'
	)
	sys.exit(1)