Autoscroll disable

[lsgalante]

I know that this was discussed in #279 and so I apologize if I am not understanding correctly.

First - is it possible to prevent the buffer from scrolling while a response is streaming? If not using a variable for chatgpt-shell itself, then maybe a comint variable? I tried messing with some comint variables but they seem to have no effect.

Second - when streaming is disabled, the buffer jumps to the bottom of the response when it comes in. I thought that this is the behavior changed in #279, but very well could be wrong.