Bump tar and webpack-mix

Removes [tar](https://github.com/isaacs/node-tar). It's no longer used after updating ancestor dependency [webpack-mix](https://github.com/devanandb/webpack-mix). These dependencies need to be updated together.


Removes `tar`

Updates `webpack-mix` from 2.0.2 to 3.0.0
- [Commits](https://github.com/devanandb/webpack-mix/commits)

---
updated-dependencies:
- dependency-name: tar
  dependency-type: indirect
- dependency-name: webpack-mix
  dependency-type: direct:development
...

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Author: dependabot[bot]