Git submodule support was lost in the refactor to use git-validate.

[serhalp]

#7 introduced git submodule support, but the refactor to use git-validate appears to have lost that feature. I opened a PR to reintroduce submodule support in git-validate here. Simply bumping git-validate afterward will reintroduce submodule support in precommit-hook.

We've been using a fork of precommit-hook pointing to that fork of git-validate for six months in several repos without issues.

Thanks1