feat: User menu trigger plugin slots. (#618)

src/desktop-header/DesktopUserMenuToggle.jsx

@@ -0,0 +1,20 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import { CaretIcon } from '../Icons';
+import Avatar from '../Avatar';
+
+const DesktopUserMenuToggle = ({ avatar, label }) => (
+  <>
+    <Avatar size="1.5em" src={avatar} alt="" className="mr-2" />
+    {label} <CaretIcon role="img" aria-hidden focusable="false" />
+  </>
+);
+
+export const DesktopUserMenuTogglePropTypes = {
+  avatar: PropTypes.string,
+  label: PropTypes.string,
+};
+
+DesktopUserMenuToggle.propTypes = DesktopUserMenuTogglePropTypes;
+
+export default DesktopUserMenuToggle;