Bump grunt from 1.5.3 to 1.6.0 (#594)

Bumps [grunt](https://github.com/gruntjs/grunt) from 1.5.3 to 1.6.0.
- [Release notes](https://github.com/gruntjs/grunt/releases)
- [Changelog](https://github.com/gruntjs/grunt/blob/main/CHANGELOG)
- [Commits](gruntjs/grunt@v1.5.3...v1.6.0)

---
updated-dependencies:
- dependency-name: grunt
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>