[DOC] resample and then apply func on time+other variables (#7725)

* [DOC] resample and then apply func on time+other variables:

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* Update doc/user-guide/time-series.rst

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Deepak Cherian <[email protected]>

Author: 3 people

doc/user-guide/time-series.rst

@@ -225,6 +225,13 @@ resampling group:
 
     ds.resample(time="6H").reduce(np.mean)
 
+You can also resample on the time dimension while applying reducing along other dimensions at the same time
+by specifying the `dim` keyword argument
+
+.. code-block:: python
+
+    ds.resample(time="6H").mean(dim=["time", "latitude", "longitude"])
+
 For upsampling, xarray provides six methods: ``asfreq``, ``ffill``, ``bfill``, ``pad``,
 ``nearest`` and ``interpolate``. ``interpolate`` extends ``scipy.interpolate.interp1d``
 and supports all of its schemes. All of these resampling operations work on both