build(deps-dev): bump html-validate from 6.3.2 to 6.4.0

Bumps [html-validate](https://gitlab.com/html-validate/html-validate) from 6.3.2 to 6.4.0.
- [Release notes](https://gitlab.com/html-validate/html-validate/tags)
- [Changelog](https://gitlab.com/html-validate/html-validate/blob/master/CHANGELOG.md)
- [Commits](https://gitlab.com/html-validate/html-validate/compare/v6.3.2...v6.4.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]