Add titles for the geometries modules in the api ref (#1848)

* add title and ref in the geometry.py api

* add title and ref in the geometry_factory.py api

src/ansys/dpf/core/geometry.py

@@ -20,7 +20,14 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-"""Module containing the different geometry objects."""
+"""
+.. _ref_geometry:
+
+Geometry
+========
+Module containing the different geometry objects.
+
+"""
 
 from ansys.dpf import core as dpf
 

src/ansys/dpf/core/geometry_factory.py

@@ -20,7 +20,14 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-"""Geometry factory module containing functions to create the different geometries."""
+"""
+.. _ref_geometry_factory:
+
+Geometry Factory
+================
+Geometry factory module containing functions to create the different geometries.
+
+"""
 
 import numpy as np