update readthedocs.yaml to version 2

readthedocs.yml

@@ -1,7 +1,22 @@
+# .readthedocs.yaml
+# Read the Docs configuration file
+# 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:
-  image: latest
+  os: ubuntu-20.04
+  tools:
+    python: "3.9"
 
-python:
-  version: 3.9
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+   configuration: doc/source/conf.py
 
-requirements_file: doc/requirements.txt
+# Optionally declare the Python requirements required to build your docs
+python:
+   install:
+   - requirements: doc/requirements.txt
+