concatenate docs style (pydata#6621)

* concatenate docs style

added and highlighted keywords as in the chapters on merge and combine.

* Update doc/user-guide/combining.rst

Co-authored-by: Maximilian Roos <5635139+max-sixty@users.noreply.github.com>

* Update doc/user-guide/combining.rst

Co-authored-by: Maximilian Roos <5635139+max-sixty@users.noreply.github.com>

Co-authored-by: Maximilian Roos <5635139+max-sixty@users.noreply.github.com>

Author: PLSeuJ

doc/user-guide/combining.rst

@@ -22,10 +22,10 @@ Combining data
 Concatenate
 ~~~~~~~~~~~
 
-To combine arrays along existing or new dimension into a larger array, you
-can use :py:func:`~xarray.concat`. ``concat`` takes an iterable of ``DataArray``
-or ``Dataset`` objects, as well as a dimension name, and concatenates along
-that dimension:
+To combine :py:class:`~xarray.Dataset`s / :py:class:`~xarray.DataArray`s along an existing or new dimension
+into a larger object, you can use :py:func:`~xarray.concat`. ``concat``
+takes an iterable of ``DataArray`` or ``Dataset`` objects, as well as a
+dimension name, and concatenates along that dimension:
 
 .. ipython:: python