Use native MediaWiki linking to help pages

There was quite a small link under the main title in Special:Notifications
which pointed to a related help page. Now the OutputPage::addHelpLink()
method is used which moves this link to the upper right corner and allows
configuring this on-wiki (instead of LocalSettings.php or so).

Bug: T101057
Change-Id: Ib4aecee8006b8d71bb3cd86f1d4ebdfee9080870

Echo.php

@@ -121,9 +121,6 @@ $wgHooks['ResourceLoaderGetConfigVars'][] = 'EchoHooks::onResourceLoaderGetConfi
 // Whether to turn on email batch function
 $wgEchoEnableEmailBatch = true;
 
-// URL for more information about the Echo notification system
-$wgEchoHelpPage = '//www.mediawiki.org/wiki/Special:MyLanguage/Help:Notifications';
-
 // Whether to use job queue to process web and email notifications, bypass the queue for now
 // since it's taking more than an hour to run in mediawiki.org, this is not acceptable for the
 // purpose of testing notification.

includes/special/SpecialNotifications.php

@@ -18,6 +18,8 @@ class SpecialNotifications extends SpecialPage {
 		$out = $this->getOutput();
 		$out->setPageTitle( $this->msg( 'echo-specialpage' )->text() );
 
+		$this->addHelpLink( 'Help:Notifications' );
+
 		$user = $this->getUser();
 		if ( $user->isAnon() ) {
 			// Redirect to login page and inform user of the need to login
@@ -136,21 +138,8 @@ class SpecialNotifications extends SpecialPage {
 	 * @return string HTML for the subtitle
 	 */
 	public function buildSubtitle() {
-		global $wgEchoHelpPage;
 		$lang = $this->getLanguage();
 		$subtitleLinks = array();
-		// More info link
-		$subtitleLinks[] = Html::element(
-			'a',
-			array(
-				'href' => $wgEchoHelpPage,
-				'id' => 'mw-echo-moreinfo-link',
-				'class' => 'mw-echo-special-header-link',
-				'title' => $this->msg( 'echo-more-info' )->text(),
-				'target' => '_blank'
-			),
-			$this->msg( 'echo-more-info' )->text()
-		);
 		// Preferences link
 		$subtitleLinks[] = Html::element(
 			'a',
@@ -162,7 +151,7 @@ class SpecialNotifications extends SpecialPage {
 			),
 			$this->msg( 'preferences' )->text()
 		);
-
+		// using pipeList to make it easier to add some links in the future
 		return $lang->pipeList( $subtitleLinks );
 	}
 

modules/nojs/mw.echo.special.less

@@ -30,22 +30,6 @@
 			opacity: 1.0;
 		}
 	}
-
-	#mw-echo-moreinfo-link {
-		display: inline-block;
-		margin: 0 3px;
-		/* @embed */
-		background-image: url(../icons/Help.png);
-		background-repeat: no-repeat;
-		background-position: 0 0;
-		filter: alpha(opacity=50);
-		opacity: 0.5;
-
-		&:hover {
-			filter: alpha(opacity=100);
-			opacity: 1.0;
-		}
-	}
 }
 
 .mw-echo-date-section {