Bump tar and node-sass in /webapp

Bumps [tar](https://github.com/npm/node-tar) to 6.1.13 and updates ancestor dependency [node-sass](https://github.com/sass/node-sass). These dependencies need to be updated together.


Updates `tar` from 4.4.13 to 6.1.13
- [Release notes](https://github.com/npm/node-tar/releases)
- [Changelog](https://github.com/npm/node-tar/blob/main/CHANGELOG.md)
- [Commits](isaacs/node-tar@v4.4.13...v6.1.13)

Updates `node-sass` from 4.13.1 to 8.0.0
- [Release notes](https://github.com/sass/node-sass/releases)
- [Changelog](https://github.com/sass/node-sass/blob/master/CHANGELOG.md)
- [Commits](sass/node-sass@v4.13.1...v8.0.0)

---
updated-dependencies:
- dependency-name: tar
  dependency-type: indirect
- dependency-name: node-sass
  dependency-type: direct:development
...

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