Bugfix/fix husky upgrade

[chenxsan]

What kind of change does this PR introduce?

Follow-up of #12630.

husky 5 works quite different from the previous version:

Important Husky v5 brings a lot of improvements but is also very different from v4. Git hooks won't work if you only upgrade husky dependency, existing config needs to be migrated too.

And here's the migration guide https://typicode.github.io/husky/#/?id=migrate-from-v4-to-v5.

Or we just downgrade to v4 as it's still available.

Did you add tests for your changes?

No need.

Does this PR introduce a breaking change?

No.

What needs to be documented once your changes are merged?

Nothing.

[webpack-bot]

For maintainers only:

• This needs to be documented (issue in webpack/webpack.js.org will be filed when merged)
• This needs to be backported to webpack 4 (issue will be created when merged)

[sokra]

ah, that explains why it's no longer working... I already wondered and thought it is only a local problem for me.

Sadly the pinst thing is a no-go, since I want github and npm version to be exactly the same and that would break it. It would also break installing from github directly since the postinstall script is executed.

Could we move husky install into the setup script instead?

[webpack-bot]

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

[chenxsan]

There's an issue here typicode/husky#868 regarding your concern of pinst. Maybe we can downgrade to v4 at the moment until they figure out a better way?