R&S '82 example refactor: extract the definition of the custom MultiBox env from a notebook cell to a separate .py file (#1542)

Author: slayoo

docs/bibliography.json

@@ -228,7 +228,8 @@
   "https://doi.org/10.3402/tellusa.v34i2.10795": {
     "usages": [
       "examples/PySDM_examples/Rozanski_and_Sonntag_1982/figs_4_5_6.ipynb",
-      "examples/PySDM_examples/Rozanski_and_Sonntag_1982/__init__.py"
+      "examples/PySDM_examples/Rozanski_and_Sonntag_1982/__init__.py",
+      "examples/PySDM_examples/Rozanski_and_Sonntag_1982/multibox.py"
     ],
     "label": "Rozanski & Sonntag 1982 (Tellus A 34)",
     "title": "Vertical distribution of deuterium in atmospheric water vapour"

examples/PySDM_examples/Rozanski_and_Sonntag_1982/__init__.py

@@ -7,3 +7,4 @@
 """
 
 # pylint: disable=invalid-name
+from PySDM_examples.Rozanski_and_Sonntag_1982.multibox import MultiBox