build: update .readthedocs.yaml

See https://blog.readthedocs.com/migrate-configuration-v2/

.readthedocs.yaml

@@ -4,3 +4,19 @@
 
 # Required
 version: 2
+
+# Set the version of Python and other tools you might need
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.11"
+
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  configuration: source/conf.py
+
+# We recommend specifying your dependencies to enable reproducible builds:
+# https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
+# python:
+#   install:
+#   - requirements: docs/requirements.txt