chore: fix docs (#106)

.readthedocs.yml

@@ -8,16 +8,14 @@ version: 2
 build:
   os: ubuntu-20.04
   tools:
-    python: "3.9"
+    python: "3.12"
   jobs:
     post_create_environment:
       # Install poetry
       - pip install poetry
-      # Tell poetry to not use a virtual environment
-      - poetry config virtualenvs.create false
     post_install:
-      # Install dependencies
-      - poetry install --with docs
+      # Install dependencies, reusing RTD virtualenv
+      - VIRTUAL_ENV=$READTHEDOCS_VIRTUALENV_PATH poetry install --with docs
 
 # Build documentation in the docs directory with Sphinx
 sphinx: