docs: fix readthedocs build (#154)

Author: cdriehuys

.readthedocs.yaml

@@ -1,18 +1,18 @@
 version: 2
 
 build:
-  os: ubuntu-22.04
-
+  os: "ubuntu-22.04"
   tools:
     python: "3.11"
-
   jobs:
     post_create_environment:
-      - pip install poetry
-      - poetry config virtualenvs.create false
-
+      # Install poetry
+      # https://python-poetry.org/docs/#installing-manually
+      - python -m pip install poetry
     post_install:
-      - poetry install --with docs
+      # Install dependencies with 'docs' dependency group
+      # https://python-poetry.org/docs/managing-dependencies/#dependency-groups
+      - VIRTUAL_ENV=$READTHEDOCS_VIRTUALENV_PATH poetry install --with docs
 
 sphinx:
   configuration: docs/conf.py