Update dockerfile to expose port 3000 for local

access

Author: NorbertLoh

frontend/peerprep/Dockerfile

@@ -19,4 +19,5 @@ COPY ./package.json package-lock.json /app/
 COPY --from=production-dependencies-env /app/node_modules /app/node_modules
 COPY --from=build-env /app/build /app/build
 WORKDIR /app
+EXPOSE 3000
 CMD ["npm", "run", "start"]