Add placement options to choices (related to #2270)

[mak448a]

Is your feature request related to a problem? Please describe.
The problem is that the "centered choices" cuts into my VN textbox, and I'd like to move it up.

Describe the solution you'd like
Add an option in styles to move the centered choices up

Describe alternatives you've considered
Shrinking the VN textbox, but then I'd have to manually change the positions of my characters

Additional context

Related to #2270