Add option to set border position: inner (default), outer, or centered

[pecoram]

It would be useful to add a parameter that allows the positioning of the border to be configurable. This parameter could accept three values: inner (default), outer, and centered.

• inner: The border is positioned within the element's bounds (default behavior).
• outer: The border is positioned outside the element's bounds.
• centered: The border is centered on the edge of the element's bounds, splitting equally between inner and outer positions.

This enhancement would provide more flexibility for UI customization.