Change `import` to `import type` to fix circular dependency (#1047)
Change `import` to `import type` to fix circular dependency (#1047)

Fixes circular dependency warning when bundling react-virtualized with rollup.

```
(!) Circular dependency: node_modules/react-virtualized/dist/es/WindowScroller/WindowScroller.js -> node_modules/react-virtualized/dist/es/WindowScroller/utils/onScroll.js -> node_modules/react-virtualized/dist/es/WindowScroller/WindowScroller.js
```
bvaughn/react-virtualized,bvaughn/react-virtualized