Add branch checkout command to Read the Docs config

Author: beckermr

.readthedocs.yaml

@@ -11,6 +11,7 @@ build:
     - git fetch --unshallow || true
     - git fetch --all --tags || true
     - if [ "${READTHEDOCS_VERSION_TYPE}" = "tag" ]; then git checkout ${READTHEDOCS_GIT_IDENTIFIER}; fi
+    - if [ "${READTHEDOCS_VERSION_TYPE}" = "branch" ]; then git checkout ${READTHEDOCS_GIT_IDENTIFIER}; fi
     - pip install uv
     - uv sync --extra docs
     - uv run sphinx-build -b html docs $READTHEDOCS_OUTPUT/html