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/mobile-header/MobileHeaderUserMenu.jsx

@@ -0,0 +1,35 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+
+const MobileHeaderUserMenu = ({ menu }) => menu.map((group) => (
+  group.items.map(({
+    type, content, href, disabled, isActive, onClick,
+  }) => (
+    <li className="nav-item" key={`${type}-${content}`}>
+      <a
+        className={`nav-link${isActive ? ' active' : ''}${disabled ? ' disabled' : ''}`}
+        href={href}
+        onClick={onClick || null}
+      >
+        {content}
+      </a>
+    </li>
+  ))
+));
+
+export const mobileHeaderUserMenuDataShape = PropTypes.arrayOf(PropTypes.shape({
+  heading: PropTypes.string,
+  items: PropTypes.arrayOf(PropTypes.shape({
+    type: PropTypes.oneOf(['item', 'menu']),
+    href: PropTypes.string,
+    content: PropTypes.string,
+    isActive: PropTypes.bool,
+    onClick: PropTypes.func,
+  })),
+}));
+
+MobileHeaderUserMenu.propTypes = {
+  menu: mobileHeaderUserMenuDataShape,
+};
+
+export default MobileHeaderUserMenu;