Add user prompt to begin installation on CLI installer

[Edhoari Setiyoso <edhoari.s@gmail.com>]

Hi,


I want to use timeshift with btrfs. The problem is that timeshift 
requires the subvolume name as '@' but installer will default to '@rootfs'.

Using GUI installer, it is possible to change this right before user 
click "Begin Installation" he/she can open tty and do some modifications.

Can we have that prompt in CLI installer so we can do additional 
modifications prior system installation?


FYI, currently once we finished partitioning it goes straight to system 
installation.


Thanks

--
Edhoari Setiyoso