build: add antarctic_plots package for import warning

src/antarctic_plots/__init__.py

@@ -0,0 +1,7 @@
+import logging
+
+logging.critical(
+    "`antarctic_plots` has been renamed to `polartoolkit`. \n"
+    "Please change any imports from `import antarctic_plots` to `import polartoolkit'\n"
+    "and updated your environment with `pip install polartoolkit` or `conda install polartoolkit`."
+    )