[css-contain-3] Export “container query length unit”

Author: fantasai

css-contain-3/Overview.bs

@@ -934,7 +934,7 @@ Style Container Features</h3>
 <h2 id="container-lengths">
 Container Relative Lengths: the ''cqw'', ''cqh'', ''cqi'', ''cqb'', ''cqmin'', ''cqmax'' units</h2>
 
-	<dfn lt="container query length">Container query length units</dfn>
+	<dfn export lt="container query length | container query length unit">Container query length units</dfn>
 	specify a length relative to the dimensions of a [=query container=].
 	Style sheets that use [=container query length=] units can more easily move components
 	from one [=query container=] to another.