Fire hook when compact language links are opened

Following on from Icc64044d, we fire the
mw.uls.compact_language_links.open hook whenever that treatment is
opened (and not only the first time that the triggering element is
clicked).

Bug: T281928
Change-Id: I6fa966c22c738ca12bcbeb0225c03f3f8394ecee

resources/js/ext.uls.launch.js

@@ -91,6 +91,8 @@ function launchULS( $trigger, languagesObject, forCLS ) {
 		},
 		onVisible: function () {
 			$trigger.addClass( 'selector-open' );
+
+			mw.hook( 'mw.uls.compact_language_links.open' ).fire();
 		},
 		languageDecorator: function ( $languageLink, language ) {
 			var element = languagesObject[ language ];