Use find-cache-dir in order to calculate the webpack default cache directory

[mistic]

This is a small PR in order to use the same behaviour to calculate the default cache dir on webpack that we are already using into the loaders. It was discussed here webpack-contrib/cache-loader#64

/CC @evilebottnawi

[webpack-bot]

For maintainers only:

• This need to be documented (issue in webpack/webpack.js.org will be filed when merged)

[webpack-bot]

Thank you for your pull request! The most important CI builds succeeded, we’ll review the pull request soon.

[alexander-akait]

Good! It is doesn't break non standard directories

[webpack-bot]

It looks like this Pull Request doesn't include enough test cases (based on Code Coverage analysis of the PR diff).

A PR need to be covered by tests if you add a new feature (we want to make sure that your feature is working) or if you fix a bug (we want to make sure that we don't run into a regression in future).

@mistic Please check if this is appliable to your PR and if you can add more test cases.

Read the test readme for details how to write test cases.

[sokra]

Thanks