fix read the docs

.readthedocs.yaml

@@ -30,7 +30,8 @@ formats:
 # Optional but recommended, declare the Python requirements required
 # to build your documentation
 # See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
-# python:
-#    install:
+python:
+  install:
+    - path: sphinx-rtd-theme
 #    - requirements: docs/requirements.txt