Option to rebind Ctrl-D from `quit` to `continue`

[dmke]

Your proposal

I'd like to have Ctrl-D behave like continue, not as quit.

This should be opt-in with a config knob, so that it can be set in ~/.rdbgrc.

Additional context

Coming from byebug, letting the program continue with Ctrl+d is deeply engrained in my muscle memory. After switching to debug, I often find myself on the Really quit? [Y/n] prompt.