Bump laravel-mix from 4.0.15 to 4.1.2

Bumps [laravel-mix](https://github.com/JeffreyWay/laravel-mix) from 4.0.15 to 4.1.2.
- [Release notes](https://github.com/JeffreyWay/laravel-mix/releases)
- [Commits](https://github.com/JeffreyWay/laravel-mix/commits)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]