docs(examples): add selection styling example

[kronberger-droid]

@fdncred Like we talked about.
I used Vi Mode since my notebook has broken arrow keys. Hope thats fine.
I also added some comments with other possible styling.

These would just have to be exposed to nushell, if we want it there.

[fdncred]

yup, i tested it and it looks good to me. In my perfect world we'd have something like ghostty has the inverts the selection colors but that sounds tricky. I think this is good for now because at least it demonstrates how it's done. Thanks!

[kronberger-droid]

@fdncred Have you tried Style::new().reverse()or do you mean something else?

[fdncred]

oh, ya. I forgot about reverse(). We can leave this example as whatever you like but for nushell I'd like to do reverse I think.