Add recipe for urchin

[traversaro]

urchin started as a mantainance fork of abandoned urdfpy package that is already in conda-forge, but then was converted to a completly different package with its own name and that can be installed side-by-side with urdfpy to continue its development.

urchin repo: https://github.com/fishbotics/urchin .
urchin PyPI: https://pypi.org/project/urchin/ .

See mmatl/urdfpy#31 for more detail.

Checklist

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[conda-forge-webservices]

Hi! This is the friendly automated conda-forge-linting service.

I wanted to let you know that I linted all conda-recipes in your PR (recipes/urchin) and found some lint.

Here's what I've got...

For recipes/urchin:

• noarch: python recipes are required to have a lower bound on the python version. Typically this means putting python >=3.6 in both host and run but you should check upstream for the package's Python compatibility.

[conda-forge-webservices]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/urchin) and found it was in an excellent condition.

[traversaro]

@conda-forge/staged-recipes @conda-forge/help-python the recipe is ready for review, thanks! It is a classical recipe for a python package already on PyPI.

[traversaro]

Thaks @ocefpaf!