Inline code setting target="_blank" in renderReferencePreview()

As discussed in Iaadcce9. This does have a few benefits:
* Less code in the already pretty big render.js file.
* The code setting the target attribute is much closer to where it
  belongs: in the file that specifies how the content of a reference
  popup should look and behave.
* The class name "mwe-popups-extract" is not mentioned in two different
  files, but in the same.

Note this changes the signature of this src/ui/templates/… file to not
return an HTML string any more, but a jQuery object. The other templates
still return strings. I believe this is fine, and not that much of a
difference anyway. The signatures don't need to be identical. And the
jQuery object still represents the exact same HTML as before.

If it helps we could change all templates/… signatures accordingly.
Could be done in this or a separate patch.

Bug: T213908
Bug: T214970
Change-Id: I05ed4b886f79c5ae748f53ab9fed965dfd217620

src/ui/renderer.js

@@ -244,19 +244,8 @@ function createDisambiguationPreview( model ) {
  * @return {ext.popups.Preview}
  */
 function createReferencePreview( model ) {
-	const $el = $(
-		$.parseHTML( renderReferencePreview( model ) )
-	);
-
-	// Make sure to not destroy existing targets, if any
-	$el.find( '.mwe-popups-extract a[href]:not([target])' ).each( ( i, a ) => {
-		a.target = '_blank';
-		// Don't let the external site access and possibly manipulate window.opener.location
-		a.rel = `${ a.rel ? `${ a.rel } ` : '' }noopener`;
-	} );
-
 	return {
-		el: $el,
+		el: renderReferencePreview( model ),
 		hasThumbnail: false,
 		isTall: false
 	};

src/ui/templates/referencePreview/referencePreview.js

@@ -9,7 +9,7 @@ const mw = mediaWiki;
 
 /**
  * @param {ext.popups.PreviewModel} model
- * @return {string} HTML string.
+ * @return {jQuery}
  */
 export function renderReferencePreview(
 	model
@@ -18,7 +18,7 @@ export function renderReferencePreview(
 		url = escapeHTML( model.url ),
 		linkMsg = escapeHTML( mw.msg( 'popups-refpreview-jump-to-reference' ) );
 
-	return renderPopup( model.type,
+	const $el = $( $.parseHTML( renderPopup( model.type,
 		`
 			<strong class='mwe-popups-title'>
 				<span class='mw-ui-icon mw-ui-icon-element mw-ui-icon-preview-reference'></span>
@@ -31,5 +31,14 @@ export function renderReferencePreview(
 				<a href='${ url }' class='mwe-popups-read-link'>${ linkMsg }</a>
 			</footer>
 		`
-	);
+	) ) );
+
+	// Make sure to not destroy existing targets, if any
+	$el.find( '.mwe-popups-extract a[href]:not([target])' ).each( ( i, a ) => {
+		a.target = '_blank';
+		// Don't let the external site access and possibly manipulate window.opener.location
+		a.rel = `${ a.rel ? `${ a.rel } ` : '' }noopener`;
+	} );
+
+	return $el;
 }