set clsx as named import instead of default

related to: lukeed/clsx#57
also related to: react-grid-layout#667

lib/Draggable.js

@@ -2,7 +2,7 @@
 import * as React from 'react';
 import PropTypes from 'prop-types';
 import ReactDOM from 'react-dom';
-import clsx from 'clsx';
+import { clsx } from 'clsx';
 import {createCSSTransform, createSVGTransform} from './utils/domFns';
 import {canDragX, canDragY, createDraggableData, getBoundPosition} from './utils/positionFns';
 import {dontSetMe} from './utils/shims';