fix: copied sphinx_rtd_theme to further shrink filesize

theme/custom_sphinx_rtd_theme/theme.conf

@@ -0,0 +1,20 @@
+[theme]
+inherit = basic
+stylesheet = css/theme.css
+pygments_style = default
+
+[options]
+canonical_url =
+analytics_id =
+analytics_anonymize_ip = False
+collapse_navigation = True
+sticky_navigation = True
+navigation_depth = 4
+includehidden = True
+titles_only =
+logo_only =
+display_version = True
+prev_next_buttons_location = bottom
+style_external_links = False
+style_nav_header_background =
+vcs_pageview_mode =