Fix missing ref support for textAlign and textColumns in theme.json s…

…chema (#63625)

* Add missing ref support for textAlign and textColumns

* Update the theme.json reference docs

Co-authored-by: ajlende <ajlende@git.wordpress.org>
Co-authored-by: t-hamano <wildworks@git.wordpress.org>
Co-authored-by: jeryj <jeryj@git.wordpress.org>