add required deps for readthedocs

Author: dniel

readthedocs.yml

@@ -13,7 +13,7 @@ sphinx:
 #formats: all
 
 # Optionally set the version of Python and requirements required to build your docs
-#python:
-#  version: 3.7
-#  install:
-#    - requirements: docs/requirements.readthedocs.txt
+python:
+  version: 3.7
+  install:
+    - requirements: docs/requirements.txt