Start the ``units`` subpackage about pyansys-geometry HOT 2 CLOSED

This task is dependent on #1. Let's get that one ready first. I'll take care of this one afterwards

from pyansys-geometry.

After @akaszynski suggested using pint, I think we could have a simple the following code in the root base __init__.py:

from pint import UnitRegistry

units = UnitRegistry()
"""Unit manager."""

This leads to the following user experience:

from ansys.geometry.core import units as u

length_A, length_B = 1.00 * u.m, 2.5 * u.inches
length_C = length_A + length_B
print(length_C)

>>> 1.0635 meter

from pyansys-geometry.