Element type is invalid

Hi,

when I try to run the storybook examples (or the package in any other of my projects), like with `git clone https://github.com/frontend-collective/react-sortable-tree && cd react-sortable-tree/ && npm i && npm run storybook`, node 15.11.0 and npm 7.6.0 I receive the following error once opening:

```
Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.

Check the render method of "App".
createFiberFromTypeAndProps@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:88488:26
createFiberFromElement@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:88511:42
reconcileSingleElement@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:77385:45
reconcileChildFibers@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:77445:57
reconcileChildren@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:79948:44
updateHostComponent@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:80470:20
callCallback@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:62195:19
dispatchEvent@[native code]
invokeGuardedCallbackDev@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:62244:29
invokeGuardedCallback@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:62299:36
beginWork$$1@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:87639:28
performUnitOfWork@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:86557:24
workLoopSync@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:86530:39
performSyncWorkOnRoot@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:86129:23
scheduleUpdateOnFiber@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:85557:28
updateContainer@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:88962:15
http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:89387:22
unbatchedUpdates@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:86292:14
legacyRenderSubtreeIntoContainer@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:89386:21
http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:358:32
Promise@[native code]
render@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:357:21
tryCatch@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:105155:44
invoke@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:105384:30
asyncGeneratorStep@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:332:103
_next@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:334:212
http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:334:369
Promise@[native code]
http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:334:108
tryCatch@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:105155:44
invoke@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:105384:30
asyncGeneratorStep@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:3832:103
_next@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:3834:212
http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:3834:369
Promise@[native code]
http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:3834:108
renderMain@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:4137:16
renderUI@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:4164:19
emit@http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:42908:39
http://0.0.0.0:3002/vendors~main.7bbb9661ec6158b26d07.bundle.js:3087:20
```

Is there an incompatibility with this nom / node / react version?

Thank you!

Regards
Max