Export ServiceWorkerRegistration's service worker registration

Author: jakearchibald

docs/index.bs

@@ -518,7 +518,7 @@ spec: webappsec-referrer-policy; urlPrefix: https://w3c.github.io/webappsec-refe
       };
     </pre>
 
-    A {{ServiceWorkerRegistration}} has a <dfn for="ServiceWorkerRegistration">service worker registration</dfn> (a [=/service worker registration=]).
+    A {{ServiceWorkerRegistration}} has a <dfn export for="ServiceWorkerRegistration">service worker registration</dfn> (a [=/service worker registration=]).
 
     <section>
       <h4 id="service-worker-registration-creation">Getting {{ServiceWorkerRegistration}} instances</h4>