Bump cross-spawn and @quasar/app-webpack in /frontend

Bumps [cross-spawn](https://github.com/moxystudio/node-cross-spawn) to 7.0.6 and updates ancestor dependency [@quasar/app-webpack](https://github.com/quasarframework/quasar). These dependencies need to be updated together.


Updates `cross-spawn` from 7.0.3 to 7.0.6
- [Changelog](https://github.com/moxystudio/node-cross-spawn/blob/master/CHANGELOG.md)
- [Commits](moxystudio/node-cross-spawn@v7.0.3...v7.0.6)

Updates `@quasar/app-webpack` from 3.12.1 to 3.15.1
- [Release notes](https://github.com/quasarframework/quasar/releases)
- [Commits](https://github.com/quasarframework/quasar/compare/@quasar/app-webpack-v3.12.1...@quasar/app-webpack-v3.15.1)

---
updated-dependencies:
- dependency-name: cross-spawn
  dependency-type: indirect
- dependency-name: "@quasar/app-webpack"
  dependency-type: direct:development
...

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

Author: dependabot[bot]