Add env setup

Author: Dumeng

.github/scripts/build.sh

@@ -13,4 +13,5 @@ error() {
 cd cpython/Doc || exit 1
 mkdir -p locales/"$LOCALE"/
 ln -sfn "$(realpath ../../docs)" locales/"$LOCALE"/LC_MESSAGES
+pip3 install -q -r requirements.txt
 make html SPHINXOPTS="-D language=$LOCALE -D gettext_compact=0 -W --keep-going" 2> >(error)