outdated/broken dependencies: Error: Cannot resolve module 'react/lib/ReactMount'

Cloning and `npm install ; npm start`, I get this:

```
$ npm install ; npm start
npm WARN deprecated chokidar@1.7.0: Chokidar 2 will break on node v14+. Upgrade to chokidar 3 with 15x less dependencies.
npm WARN deprecated fsevents@1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.
npm WARN deprecated core-js@1.2.7: core-js@<2.6.8 is no longer maintained. Please, upgrade to core-js@3 or at least to actual version of core-js@2.
npm WARN deprecated minimatch@2.0.10: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
npm notice created a lockfile as package-lock.json. You should commit this file.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@^1.0.0 (node_modules/chokidar/node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
npm WARN The package prop-types is included as both a dev and production dependency.

added 479 packages from 364 contributors and audited 2961 packages in 10.24s

2 packages are looking for funding
run `npm fund` for details

found 35 vulnerabilities (12 low, 22 high, 1 critical)
run `npm audit fix` to fix them, or `npm audit` for details

> react-treeview@0.4.7 start /tmp/react-treeview
> NODE_ENV=development node server.js

Listening at localhost:3000
Hash: c2b9c2c74bdb4c783932
Version: webpack 1.15.0
Time: 1673ms
Asset Size Chunks Chunk Names
bundle.js 1.5 MB 0 main
chunk {0} bundle.js (main) 1.39 MB [rendered]

ERROR in ./demos/index.js
Module not found: Error: Cannot resolve module 'react/lib/ReactMount' in /tmp/react-treeview/demos
@ ./demos/index.js 1:250-281

ERROR in ./demos/controlled.js
Module not found: Error: Cannot resolve module 'react/lib/ReactMount' in /tmp/react-treeview/demos
@ ./demos/controlled.js 1:250-281

ERROR in ./demos/uncontrolled.js
Module not found: Error: Cannot resolve module 'react/lib/ReactMount' in /tmp/react-treeview/demos
@ ./demos/uncontrolled.js 1:250-281

ERROR in ./src/react-treeview.jsx
Module not found: Error: Cannot resolve module 'react/lib/ReactMount' in /tmp/react-treeview/src
@ ./src/react-treeview.jsx 1:250-281
webpack: Failed to compile.
```

I have tried a lot of things found around the web, like most things suggested here https://stackoverflow.com/questions/40652327/module-not-found-error-cannot-resolve-module-react-lib-reactmount which led to different errors, and trying to solve them trying things suggested here https://github.com/gaearon/react-hot-loader/issues/569 which led to different errors described here https://github.com/gaearon/react-hot-loader/issues/1411.

Maybe it would be best if someone with actual knowledge about the npm ecosystem could update this repo. It seems quite outdated.