docs: fix update theme property to a reactive property * update sfc-css-features.md Update theme to reactive property * docs: make example consistent with ref recommendation as standard --------- Co-authored-by: Ben Hong <[email protected]> (#2009)

docs: fix update theme property to a reactive property * update sfc-css-features.md Update theme to reactive property * docs: make example consistent with ref recommendation as standard --------- Co-authored-by: Ben Hong <[email protected]> (#2009) #2680