Update coveralls requirement from ^2.11.6 to ^3.0.2
Update coveralls requirement from ^2.11.6 to ^3.0.2

Updates the requirements on [coveralls](https://github.com/nickmerwin/node-coveralls) to permit the latest version.
- [Release notes](https://github.com/nickmerwin/node-coveralls/releases)
- [Commits](https://github.com/nickmerwin/node-coveralls/commits/3.0.2)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
hexojs/hexo-generator-category