readthedocs poetry extra fix

Author: p1c2u

.readthedocs.yaml

@@ -5,10 +5,13 @@ sphinx:
 
 formats: all
 
-python:
-  version: 3.8
-  install:
-    - method: pip
-      path: .
-      extra_requirements:
-        - docs
+build:
+  os: ubuntu-20.04
+  tools:
+    python: "3.9"
+  jobs:
+    post_create_environment:
+      - pip install poetry
+      - poetry config virtualenvs.create false
+    post_install:
+      - poetry install --with docs