[css-regions] Export key definitions

Author: frivoal

css-regions/Overview.bs

@@ -254,7 +254,7 @@ CSS Regions concepts</h2>
 <h3 id="regions">
 Regions</h3>
 
-	A <dfn>CSS Region</dfn>
+	A <dfn export>CSS Region</dfn>
 	is a block container
 	that has an associated
 	<em><a>named flow</a></em>
@@ -263,7 +263,7 @@ Regions</h3>
 <h3 id="region-chain-section">
 Region chain</h3>
 
-	A <dfn>region chain</dfn>
+	A <dfn export>region chain</dfn>
 	is the sequence of regions
 	that are associated with
 	a <a>named flow</a>.