Improve HK sidebar and restore nested content scrolling

src/messages/nl.json

@@ -1047,6 +1047,9 @@
 				"backToSite": "Terug naar site",
 				"expandAll": "Alles openen",
 				"collapseAll": "Alles sluiten",
+				"searchMenu": "Zoeken in menu…",
+				"clearMenuSearch": "Menuzoekopdracht wissen",
+				"noMenuResults": "Geen pagina’s gevonden.",
 				"housekeeping": "Permissie-archief",
 				"hotelManagementPanel": "Hotelbeheerpaneel",
 				"rankLabel": "Rang {rank}",