updated Dockerfile

frontend/Dockerfile

@@ -1,4 +1,4 @@
-FROM node:12
+FROM node:12 AS build
 
 ADD . /app
 WORKDIR /app
@@ -6,3 +6,8 @@ RUN rm /app/.npmrc
 
 # install frontend
 RUN yarn install && yarn run build:docker
+
+FROM alpine:3.14
+
+# copy files
+COPY --from=build /app/dist /app/dist