docs: Add See Also sections for datetime docstrings

Author: Ned Western

py-polars/src/polars/series/datetime.py

@@ -1917,6 +1917,10 @@ def truncate(self, every: str | dt.timedelta | IntoExprColumn) -> Series:
         Series
             Series of data type :class:`Date` or :class:`Datetime`.
 
+        See Also
+        --------
+        Series.dt.round : Map to the nearest bucket.
+
         Examples
         --------
         >>> from datetime import timedelta, datetime
@@ -2030,6 +2034,10 @@ def round(self, every: str | dt.timedelta | IntoExprColumn) -> Series:
         not be 24 hours, due to daylight savings). Similarly for "calendar week",
         "calendar month", "calendar quarter", and "calendar year".
 
+        See Also
+        --------
+        Series.dt.truncate : Map to start of the bucket.
+
         Examples
         --------
         >>> from datetime import timedelta, datetime