Bump html-proofer from 3.18.5 to 3.18.6
Bumps [html-proofer](https://github.com/gjtorikian/html-proofer) from 3.18.5 to 3.18.6. - [Release notes](https://github.com/gjtorikian/html-proofer/releases) - [Commits](https://github.com/gjtorikian/html-proofer/compare/v3.18.5...v3.18.6)