Update markdownlint requirement from ^0.15.0 to ^0.16.0
Update markdownlint requirement from ^0.15.0 to ^0.16.0

Updates the requirements on [markdownlint](https://github.com/DavidAnson/markdownlint) to permit the latest version.
- [Release notes](https://github.com/DavidAnson/markdownlint/releases)
- [Commits](https://github.com/DavidAnson/markdownlint/compare/v0.15.0...v0.16.0)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
sagiegurari/grunt-markdownlint