This controls both how the origin is determined for the Style::position field,
and whether or not the item will be controlled by flexbox’s layout algorithm.
WARNING: this enum follows the behavior of CSS’s position property,
which can be unintuitive.
Position::Relative is the default value, in contrast to the default behavior in CSS.
The offset is computed relative to the final position given by the layout algorithm.
Offsets do not affect the position of any other items; they are effectively a correction factor applied at the end.
The offset is computed relative to this item’s closest positioned ancestor, if any.
Otherwise, it is placed relative to the origin.
No space is created for the item in the page layout, and its size will not be altered.
WARNING: to opt-out of layouting entirely, you must use Display::None instead on your Style object.