Add support for new viewport unit in Size class

[lserio]

Hi everyone,
it might be useful to add support for new viewport units (svh, lvh, svw, lvw, dvh, dvw) into the ABSOLUTE_SIZE_UNITS array in src\Value\Size.php

const ABSOLUTE_SIZE_UNITS = ['px', 'cm', 'mm', 'mozmm', 'in', 'pt', 'pc', 'vh', 'vw', 'vmin', 'vmax', 'rem'];

https://redstapler.co/all-css-viewport-units-svh-lvh-svw-lvw-dvh-dvw-explained/