Syntax
/* Single keyword */
text-decoration-thickness: auto;
text-decoration-thickness: from-font;
/* length */
text-decoration-thickness: 0.1em;
text-decoration-thickness: 3px;
/* percentage */
text-decoration-thickness: 10%;
/* Global values */
text-decoration-thickness: inherit;
text-decoration-thickness: initial;
text-decoration-thickness: revert;
text-decoration-thickness: unset;