feat: add frontend-plugin-framework slots (#545)

Add the following `frontend-plugin-framework` slots:
* `logo_slot`
* `desktop_main_menu_slot`
* `desktop_secondary_menu_slot`
* `mobile_main_menu_slot`
* `course_info_slot`
* `learning_help_slot`
* `desktop_logged_out_items_slot`
* `mobile_logged_out_items_slot`
* `mobile_user_menu_slot`
* `desktop_user_menu_slot`
* `learning_user_menu_slot`
* `learning_logged_out_items_slot`
* `desktop_header_slot`

src/learning-header/LearningHeaderUserMenuItems.jsx

@@ -0,0 +1,21 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+
+import { Dropdown } from '@openedx/paragon';
+
+const LearningHeaderUserMenuItems = ({ items }) => items.map((item) => (
+  <Dropdown.Item href={item.href}>
+    {item.message}
+  </Dropdown.Item>
+));
+
+export const learningHeaderUserMenuDataShape = {
+  items: PropTypes.arrayOf(PropTypes.shape({
+    message: PropTypes.string,
+    href: PropTypes.string,
+  })),
+};
+
+LearningHeaderUserMenuItems.propTypes = learningHeaderUserMenuDataShape;
+
+export default LearningHeaderUserMenuItems;