enable autosectionlabel extension for internal linking

docs/conf.py

@@ -29,7 +29,7 @@
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = []
+extensions = ['sphinx.ext.autosectionlabel']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']