Add reference tag to Hatch style reference

Author: rcomer

galleries/examples/shapes_and_collections/hatch_style_reference.py

@@ -64,3 +64,7 @@ def hatches_plot(ax, h):
 #    - `matplotlib.patches.Rectangle`
 #    - `matplotlib.axes.Axes.add_patch`
 #    - `matplotlib.axes.Axes.text`
+#
+# .. tags::
+#
+#    purpose: reference