Bump karma-webpack from 1.8.1 to 2.0.13

Bumps [karma-webpack](https://github.com/webpack-contrib/karma-webpack) from 1.8.1 to 2.0.13.
- [Release notes](https://github.com/webpack-contrib/karma-webpack/releases)
- [Changelog](https://github.com/ryanclark/karma-webpack/blob/master/CHANGELOG.md)
- [Commits](codymikol/karma-webpack@v1.8.1...v2.0.13)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]