[css-highlight-pseudo-1] Export term

Author: fantasai

css-highlight-api-1/Overview.bs

@@ -246,7 +246,7 @@ Registering Custom Highlights</h3>
 		the passed-in [=custom highlight name=] as <var ignore>keyArg</var>,
 		and the passed-in highlight as <var ignore>valueArg</var>.
 
-		The <dfn>custom highlight name</dfn> assigned to a [=custom highlight=] when it is [=registered=]
+		The <dfn export>custom highlight name</dfn> assigned to a [=custom highlight=] when it is [=registered=]
 		is used to identify the highlight during styling (see [[#styling-highlights]]).
 
 	Note: When registering a [=custom highlight=],