Update Dockerfile.main.alpine

Author: saul-gush

docker-build/Dockerfile.main.alpine

@@ -27,6 +27,7 @@ ADD frontend/craco.config.js /node/craco.config.js
 ADD frontend/package.json /node/package.json
 
 RUN yarn add global env-cmd
+RUN yarn
 RUN yarn builddocker