Leggedsnake

- ``setup.cfg`` was not PyPi compatible. Removed mail (use GitHub!), we now
explicitly say that ``README.md`` is markdown (PyPi is conservative)

- ``CODE_OF_CONDUCT.md`` to help community.
- ``LICENSE`` MIT License.
- ``MANIFEST.in`` to include more files.
- ``README.md`` as a very minimal version.
- ``environment.yml`` with matplotlib, numpy, and pygad requirement.
- ``examples/strider.py`` a complete demo with Strider linkage.
- ``leggedsnake/__init__.py``.
- ``leggedsnake/dynamiclinkage.py``.
- ``leggedsnake/geneticoptimizer.py``.
- ``leggedsnake/physicsengine.py``.
- ``leggedsnake/show_evolution.py`` just a legacy package, no utility.
- ``leggedsnake/tests/test_utility.py`` untested test case
- ``leggedsnake/utility.py`` contain some useful evaluation function (``step``
and ``stride``) and a broken GeoGebra interface.
- ``walker.py`` defines the ``Walker`` object.
- ``pyproject.toml``.
- ``setup.cfg``.
- ``setup.py`` empty, for compatibility purposes only.
- ``tox.ini`` tox with Python 3.7 and 3.8.

Basic version, supporting Genetic Algorithm optimization, but with various
problems.