fix(compatibility): full screen scroll region

[imsnif]

Fixes #797

This was happening because when the scroll region is set to the full viewport, it should send lines to the scrollbuffer rather than swallowing them.

In our codebase, we treat the scroll region as an Option - and this is not entirely correct according to https://vt100.net/docs/vt510-rm/DECSTBM.html

At some point we should change the scroll region to always be there and default to the first and last line of the viewport. This is however quite a big change, so for now I solved this case with a conditional.

[Lillecarl]

Good work, not that anyone's asking but I'd say this deserves a release on it's own, scrollback is quite essential 😄

[imsnif]

Definitely planning on it for next week, sorry - I'm just quite swamped at the moment.
Now that I know what the problem is, as a temporary workaround you can do echo -e "\033[r" whenever this happens. If for some reason that doesn't work, you could also do "reset" - the latter will kill the current scrollback but at least you won't have to restart the pane.

[mhristache]

I am still getting this issue with zellij 0.40.1, not sure what the trigger is but I mainly get into it when using ssh sessions (zellij running on my machine from which I ssh to other machines). reset is fixing it, echo -e "\033[r" doesn't