[FEAT] Global decimal point setting

[Kingproone]

Description

at the moment you have to specify each categories decimal precision one by one, would be nice to just have a 'gobal' or 'all' variable that controls them

Motivation

cleaner config files, since i like if my values are consistent

Additional context

https://github.com/Kingproone/dotfiles/blob/main/home/%24USER/.config/fastfetch/config.jsonc

"display": {
                "separator": " ",
                "fraction": {"ndigits":2},
                "temp":     {"ndigits":2},
                "freq":     {"ndigits":2},
                "percent":  {"ndigits":2},
                "size":     {"ndigits":2}
           },

could change to something like this:

"display": {
                "separator": " ",
                "global": {"ndigits":2},
           },