Use Read the Docs command to build Sphinx documents in parallel

.readthedocs.yaml

@@ -8,14 +8,18 @@ build:
   os: "ubuntu-22.04"
   tools:
     python: "3.10"
+  commands:
+    - python -mvirtualenv $READTHEDOCS_VIRTUALENV_PATH
+    - python -m pip install --upgrade --no-cache-dir pip setuptools
+    - python -m pip install --upgrade --no-cache-dir sphinx readthedocs-sphinx-ext
+    - python -m pip install --exists-action=w --no-cache-dir -r requirements.txt
+    - cat conf.py
+    - python -m sphinx -j auto -T -b html -d _build/doctrees -D language=en . $READTHEDOCS_OUTPUT/html
 
 python:
   install:
     - requirements: requirements.txt
 
-sphinx:
-  configuration: conf.py
-
 # Possible options: htmlzip, pdf, epub
 # All disabled for now:
 # - single-page htmlzip is too big to be usable, and requires too much memory.