Add index and modindex to sidebar

- https://stackoverflow.com/questions/25243482/how-to-add-sphinx-generated-index-to-the-sidebar-when-using-read-the-docs-theme

docs/conf.py

@@ -68,7 +68,9 @@ autoapi_ignore = [
 
 # Add any paths that contain templates here, relative to this directory.
 autoapi_template_dir = 'templates'
+autoapi_root = 'api'
 
+templates_path = ['templates']
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.