Update readthedocs config to version 2

.readthedocs.yml

@@ -1,6 +1,17 @@
-requirements_file: docs/requirements.txt
-
+# see also: https://docs.readthedocs.io/en/stable/config-file/v2.html#supported-settings
+version: 2
 formats:
     - htmlzip
     - pdf
     - epub
+build:
+    os: ubuntu-22.04
+    tools:
+        python: "3.11"
+sphinx:
+    builder: html
+    configuration: docs/source/conf.py
+    fail_on_warning: false
+python:
+    install:
+        - requirements: docs/requirements.txt