Bump shelljs and xo

Removes [shelljs](https://github.com/shelljs/shelljs). It's no longer used after updating ancestor dependency [xo](https://github.com/xojs/xo). These dependencies need to be updated together.


Removes `shelljs`

Updates `xo` from 0.18.2 to 0.60.0
- [Release notes](https://github.com/xojs/xo/releases)
- [Commits](xojs/xo@v0.18.2...v0.60.0)

---
updated-dependencies:
- dependency-name: shelljs
  dependency-type: indirect
- dependency-name: xo
  dependency-type: direct:development
...

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

Author: dependabot[bot]