Update RTD config

.readthedocs.yaml

@@ -1,15 +1,19 @@
-# .readthedocs.yaml
-# Read the Docs configuration file
+# Read the Docs configuration file for MkDocs projects
 # See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
 
 # Required
 version: 2
 
+# Set the version of Python and other tools you might need
+build:
+  os: ubuntu-20.04
+  tools:
+    python: "3.7"
+
 mkdocs:
   configuration: mkdocs.yml
 
-# Optionally set the version of Python and requirements required to build your docs
+# Optionally declare the Python requirements required to build your docs
 python:
-  version: "3.7"
   install:
-    - requirements: docs/requirements.txt
+  - requirements: docs/requirements.txt