update readthedocs config

.readthedocs.yaml

@@ -17,7 +17,7 @@ sphinx:
 # Optionally, but recommended,
 # declare the Python requirements required to build your documentation
 # See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
-# python:
-#    install:
-#    - requirements: docs/requirements.txt
+python:
+   install:
+   - requirements: docs/requirements.txt
         

docs/requirements.txt

@@ -0,0 +1 @@
+sphinx_rtd_theme