doc: add graphviz extension
graphviz lets us create graphic images via a text language rather than
creating drawings in other tools (eliminating the need to keep the
sources for the images available, such as a powerpoint file).
@@ -30,7 +30,9 @@ sys.path.insert(0, os.path.abspath('.'))
# Add any Sphinx extension module names here, as strings. They can be
# extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
# ones.
-extensions = ['breathe']
+extensions = ['breathe', 'sphinx.ext.graphviz']
+
+graphviz_output_format='svg'
# Add any paths that contain templates here, relative to this directory.
templates_path = ['_templates']
