Add zeitwerk:check action runner

.github/workflows/test-core.yml

@@ -80,6 +80,8 @@ jobs:
     steps:    
     - uses: actions/checkout@v2
     - uses: ruby/setup-ruby@v1
+      with:
+        bundler-cache: true
     - uses: actions/setup-node@v2
       with:
         node-version: '14'

docker/ci/entrypoint.sh

@@ -57,6 +57,7 @@ fi
 
 if [ "$1" == "run-units" ]; then
 	shift
+	execute "time bundle exec rake zeitwerk:check"
 	execute "cd frontend && npm install && npm run test"
 	execute "time bundle exec rspec -I spec_legacy spec_legacy"
 	if ! execute "time bundle exec rake parallel:units" ; then