Bump laravel-mix from 6.0.11 to 6.0.13
Bump laravel-mix from 6.0.11 to 6.0.13

Bumps [laravel-mix](https://github.com/JeffreyWay/laravel-mix) from 6.0.11 to 6.0.13.
- [Release notes](https://github.com/JeffreyWay/laravel-mix/releases)
- [Changelog](https://github.com/JeffreyWay/laravel-mix/blob/master/CHANGELOG.md)
- [Commits](https://github.com/JeffreyWay/laravel-mix/commits)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
firefly-iii/firefly-iii,firefly-iii/firefly-iii,JC5/firefly-iii,JC5/firefly-iii,firefly-iii/firefly-iii,firefly-iii/firefly-iii