added type doc to menu related files

src/app/shared/menu/menu-item.decorator.ts

@@ -0,0 +1,26 @@
+import { MenuItemType } from './initial-menus-state';
+
+const menuMenuItemComponentMap = new Map();
+
+/**
+ * Decorator function to link a MenuItemType to a Component
+ * @param {MenuItemType} type The MenuItemType of the MenuSection's model
+ * @returns {(sectionComponent: GenericContructor) => void}
+ */
+export function rendersMenuItemForType(type: MenuItemType) {
+  return function decorator(sectionComponent: any) {
+    if (!sectionComponent) {
+      return;
+    }
+    menuMenuItemComponentMap.set(type, sectionComponent);
+  };
+}
+
+/**
+ * Retrieves the Component matching a given MenuItemType
+ * @param {MenuItemType} type The given MenuItemType
+ * @returns {GenericConstructor} The constructor of the Component that matches the MenuItemType
+ */
+export function getComponentForMenuItemType(type: MenuItemType) {
+  return menuMenuItemComponentMap.get(type);
+}