adjust readthedocs for use with dependency groups

.readthedocs.yaml

@@ -2,23 +2,26 @@
 # Read the Docs configuration file
 # See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
 
-# Note: I used https://github.com/readthedocs/readthedocs.org/issues/4912#issuecomment-664002569 for inspiration
+# Note: I used https://docs.readthedocs.io/en/stable/build-customization.html#install-dependencies-with-poetry for inspiration
 
 version: 2
 
 build:
   os: "ubuntu-22.04"
   tools:
-    python: "3.7"
+    python: "3.8"
+  jobs:
+    post_create_environment:
+      # Install poetry
+      # https://python-poetry.org/docs/#installing-manually
+      - pip install poetry
+      # Tell poetry to not use a virtual environment
+      - poetry config virtualenvs.create false
+    post_install:
+      # Install dependencies with 'docs' dependency group
+      # https://python-poetry.org/docs/managing-dependencies/#dependency-groups
+      - poetry install --with docs
 
 sphinx:
   configuration: docs/conf.py
   fail_on_warning: true
-
-python:
-  install:
-    - method: pip
-      path: .
-      extra_requirements:
-        - docs
-        - files