Use make-dir instead of mkdirp

[pustovalov]

Summary

warning @loadable/webpack-plugin > mkdirp@0.5.4: Legacy versions of mkdirp are no longer supported. Please update to mkdirp 1.x. (Note that the API surface has changed to use Promises in 1.x.)

https://github.com/isaacs/node-mkdirp/blob/master/CHANGELOG.md

also

[theKashey]

Ok, so updated mkdirp requires node>=10, and we have to follow.

[pustovalov]

Found one more inconsistency, webpack 4 supports "node": ">=6.11.5"
https://github.com/webpack/webpack/blob/webpack-4/package.json#L88

I see a few options:

1. Update mkdirp and drop node 8
2. Switch to another package: https://github.com/sindresorhus/make-dir
   like babel did:
   babel/babel-loader@47958ca

[theKashey]

The second option sounds better, and the make-dir library is actually doing only what we need, not a dozen other things.

[gregberge]

Thanks!