update CI to use new tidy extra checks for rustdoc js

Author: lolbinarycat

src/ci/docker/host-x86_64/tidy/Dockerfile

@@ -45,4 +45,4 @@ RUN bash -c 'npm install -g eslint@$(cat /tmp/eslint.version)'
 # NOTE: intentionally uses python2 for x.py so we can test it still works.
 # validate-toolstate only runs in our CI, so it's ok for it to only support python3.
 ENV SCRIPT TIDY_PRINT_DIFF=1 python2.7 ../x.py test --stage 0 \
-  src/tools/tidy tidyselftest --extra-checks=py,cpp
+  src/tools/tidy tidyselftest --extra-checks=py,cpp,js