new 2D advection diffusion example (#427)

Co-authored-by: Sylwester Arabas <sylwester.arabas@agh.edu.pl>
Co-authored-by: Paweł Magnuszewski <47724273+pawelmagnu@users.noreply.github.com>
Co-authored-by: pawel <pawel.magnu@gmail.com>

.github/workflows/tests+pypi.yml

@@ -236,6 +236,7 @@ jobs:
         run: |
           mkdir -p /home/runner/work/_temp/_github_home/figures
           mv /tmp/pytest-of-runner/pytest-current/test_run_notebooks_examples_*/fig_4.svg /home/runner/work/_temp/_github_home/figures
+          mv /tmp/pytest-of-runner/pytest-current/test_run_notebooks_examples_*/advection_diffusion.gif /home/runner/work/_temp/_github_home/figures
         
       - if: ${{ github.ref == 'refs/heads/main' && matrix.platform == 'ubuntu-latest' && matrix.python-version == '3.11'}}
         uses: eine/tip@master

examples/PyMPDATA_examples/__init__.py

@@ -1,6 +1,8 @@
 """
 PyMPDATA_examples package includes common Python modules used in PyMPDATA smoke tests
-and in example notebooks (but the package wheels do not include the notebooks)
+and in example notebooks (but the package wheels do not include the notebooks).
+![adv_diff](https://github.com/open-atmos/PyMPDATA/releases/download/tip/advection_diffusion.gif)
+
 """
 
 from importlib.metadata import PackageNotFoundError, version

examples/PyMPDATA_examples/advection_diffusion_2d/__init__.py

@@ -0,0 +1,3 @@
+"""
+PyMPDATA 2D advection-diffusion example with gif creation.
+"""

examples/setup.py

@@ -34,6 +34,7 @@ def get_long_description():
         "pint",
         "joblib",
         "sympy",
+        "imageio",
     ],
     author="https://github.com/open-atmos/PyMPDATA/graphs/contributors",
     license="GPL-3.0",