Help: Add option for disabling antialising of fonts

For the backends that we can do it for (litehtml, QTextBrowser).

Fixes: QTCREATORBUG-12177
Change-Id: If64a279f74f878b6797bf43d8129058c6183919b
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Kai Köhne <kai.koehne@qt.io>

src/plugins/help/helpplugin.cpp

@@ -374,6 +374,13 @@ HelpViewer *HelpPlugin::createHelpViewer()
     connect(LocalHelpManager::instance(), &LocalHelpManager::fontZoomChanged,
             viewer, &HelpViewer::setFontZoom);
 
+    // initialize antialias
+    viewer->setAntialias(LocalHelpManager::antialias());
+    connect(LocalHelpManager::instance(),
+            &LocalHelpManager::antialiasChanged,
+            viewer,
+            &HelpViewer::setAntialias);
+
     viewer->setScrollWheelZoomingEnabled(LocalHelpManager::isScrollWheelZoomingEnabled());
     connect(LocalHelpManager::instance(), &LocalHelpManager::scrollWheelZoomingEnabledChanged,
             viewer, &HelpViewer::setScrollWheelZoomingEnabled);