feat: add save instruction to +list-themes

[Aaron-212]

Close #4731

[jainhitesh9998]

@Aaron-212 @mitchellh.

ghostty doesnt create a config file by default right?
I'm using it in mac and had to create it manually at either XDG or ~/.config/ghostty/config.

if this specific reference can be added in the +list-themes functionality or a default empty config is created during installation, it'll make things more accessible to a lot of people.

themes is probably only customization most do.

i have had a few of my friends try ghostty.
the terminal enthusiasts customized it to their liking really fast. the occasional users took some time going through the docs or needed help.

[pluiedev]

ghostty doesnt create a config file by default right? I'm using it in mac and had to create it manually at either XDG or ~/.config/ghostty/config.

It does. #3460

[mitchellh]

Note @pluiedev there's some bugs in 1.0.1 where if the dir doesn't exist we don't create the file. I think these were resolved on tip though.