DOC: Update whats_new.rst

doc/whats_new.rst

@@ -22,6 +22,8 @@ Changelog
 
 - Store :class:`~hnn_core.Cell` instances in :class:`~hnn_core.Network`'s :attr:`~/hnn_core.Network.cells` attribute by `Ryan Thorpe`_ in `#321 <https://github.com/jonescompneurolab/hnn-core/pull/321>`_
 
+- Add probability argument to :func:`~hnn_core.Network.add_connection`. Connectivity patterns can also be visualized with :func:`~hnn_core.viz.plot_connectivity_matrix`, by `Nick Tolley`_ in `#318 <https://github.com/jonescompneurolab/hnn-core/pull/318>`_
+
 Bug
 ~~~
 
@@ -37,6 +39,8 @@ API
 - New API for accessing and modifying :class:`~hnn_core.Cell` attributes (e.g., synapse and biophysics parameters) as cells are now instantiated from template cells specified
   in a :class:`~hnn_core.Network` instance's :attr:`~/hnn_core.Network.cell_types` attribute by `Ryan Thorpe`_ in `#321 <https://github.com/jonescompneurolab/hnn-core/pull/321>`_
 
+- New API for network creation. The default network is now created with ``net = default_network(params)``, by `Nick Tolley`_ in `#318 <https://github.com/jonescompneurolab/hnn-core/pull/318>`_
+
 .. _0.1:
 
 0.1