add changelog entry

Signed-off-by: Victor Garcia Reolid <victor@seita.nl>

documentation/changelog.rst

@@ -12,6 +12,7 @@ New features
 
 * Add command ``flexmeasures edit transfer-ownership`` to transfer the ownership of an asset and its children from one account to another[see `PR #983 <https://github.com/FlexMeasures/flexmeasures/pull/983>`_]
 * Support defining the ``site-power-capacity``, ``site-consumption-capacity`` and ``site-production-capacity`` as a sensor in the API and CLI [see `PR #985 <https://github.com/FlexMeasures/flexmeasures/pull/985>`_]
+* Support defining inflexible power sensors with arbitrary power and energy units [see `PR #1007 <https://github.com/FlexMeasures/flexmeasures/pull/1007>`_]
 
 
 Infrastructure / Support