tui-scrollview: make size and page_size public

[pmielle]

Hello,

I have a feature request for tui-scrollview:

I would like to know if there is a reason why ScrollViewState has a getter for "offset" (*) but not for "size" and "page_size".
I am writing some logic that would need to get these (scroll an element into view depending on if it is offscreen or not..)

thanks! and thanks for the work on this crate, too

(*)

tui-widgets/tui-scrollview/src/state.rs

Line 33 in 514c4ac

pub const fn offset(&self) -> Position {