docs: add sphinx_rtd_theme to extensions (fixes js)

docs/conf.py

@@ -15,7 +15,9 @@ author = 'ccc'
 # -- General configuration ---------------------------------------------------
 # https://www.sphinx-doc.org/en/master/usage/configuration.html#general-configuration
 
-extensions = []
+extensions = [
+    'sphinx_rtd_theme',
+]
 
 templates_path = ['_templates']
 exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']