build(docker): reduce image size (#2392)

Dockerfile

@@ -26,7 +26,7 @@ RUN yarn build
 # remove development dependencies
 RUN yarn install --production --ignore-scripts --prefer-offline
 
-RUN rm -rf src server
+RUN rm -rf src server .next/cache
 
 RUN touch config/DOCKER
 
@@ -37,7 +37,7 @@ FROM node:14.18-alpine
 
 WORKDIR /app
 
-RUN apk add --no-cache tzdata tini
+RUN apk add --no-cache tzdata tini && rm -rf /tmp/*
 
 # copy from build image
 COPY --from=BUILD_IMAGE /app ./