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/desktop-header/DesktopHeaderUserMenu.jsx

@@ -0,0 +1,39 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+
+const DesktopHeaderUserMenu = ({ menu }) => menu.map((group, index) => (
+  // eslint-disable-next-line react/jsx-no-comment-textnodes,react/no-array-index-key
+  <React.Fragment key={index}>
+    {group.heading && <div className="dropdown-header" role="heading" aria-level="1">{group.heading}</div>}
+    {group.items.map(({
+      type, content, href, disabled, isActive, onClick,
+    }) => (
+      <a
+        className={`dropdown-${type}${isActive ? ' active' : ''}${disabled ? ' disabled' : ''}`}
+        key={`${type}-${content}`}
+        href={href}
+        onClick={onClick || null}
+      >
+        {content}
+      </a>
+    ))}
+    {index < menu.length - 1 && <div className="dropdown-divider" role="separator" />}
+  </React.Fragment>
+));
+
+export const desktopUserMenuDataShape = 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,
+  })),
+}));
+
+DesktopHeaderUserMenu.propTypes = {
+  menu: desktopUserMenuDataShape,
+};
+
+export default DesktopHeaderUserMenu;