Bump ember-cli-addon-docs from 0.6.1 to 0.6.12

Bumps [ember-cli-addon-docs](https://github.com/ember-learn/ember-cli-addon-docs) from 0.6.1 to 0.6.12.
- [Release notes](https://github.com/ember-learn/ember-cli-addon-docs/releases)
- [Changelog](https://github.com/ember-learn/ember-cli-addon-docs/blob/master/CHANGELOG.md)
- [Commits](ember-learn/ember-cli-addon-docs@v0.6.1...v0.6.12)