Remove dependency on gulp

[eseliger]

As per gulp plugin guidelines, there should be no dependency on gulp itself, for a good reason. So removing it as a dependency and adding it as a devDependency should be viable in my opinion. I can open a PR with this if you agree

[JemiloII]

@eseliger gulp should be a peer dependency as the package requires it, however, as a peer dependency, we can update the module with our own security updates as needed.

[eseliger]

If I get your point correctly, you are worried about using the wrong version of gulp with this plugin? If not, please correct me.
If that is what you are saying, you can always define a range of valid gulp versions compatible with gulp-nodemon
So you can still ensure gulp being the version you want it to be 🤔