Don't force requirement on types-python-dateutil

[mredaelli]

Feature Request

A project I work on follows the usual pattern of having two requirements file, one for production environments and one for development, compiled by pip-tools.

I just noticed that arrow adds the types-python-dateutil package to my prod requirements.txt.

Since typing information should not be necessary at runtime, I think the installation of that package should be left to the user who wants it.

[bnavigator]

As a contributor to the maintenance of the openSUSE Tumbleweed Linux Python Stack, I wholeheartedly agree.

https://build.opensuse.org/request/show/1138316

[sanderr]

I also feel like this should be a development package. Perhaps it can be exposed as an optional extra arrow[dev] or arrow[types]? This way you can still make abstraction of your typing requirements for library users, while keeping it contained to those that specifically request it.