add builder stage, update yarn-lts docker image

Dockerfile

@@ -1,10 +1,19 @@
-FROM node:lts-alpine3.12
+FROM node:lts-alpine3.15 AS builder
+RUN apk add gifsicle libpng libpng-dev libtool file nasm autoconf automake pkgconfig make g++ python2
 RUN mkdir /data
-COPY ./ /data
 WORKDIR /data
+COPY ./ ./
+RUN yarn install && yarn run build
+
+FROM node:lts-alpine3.15
+RUN mkdir /data
+WORKDIR /data
+COPY --from=builder /data/package.json .
+COPY --from=builder /data/src/main.js ./src/
+COPY --from=builder /data/dist ./dist
 RUN yarn install --production
 RUN adduser --disabled-password --gecos "" slowdowner
 RUN chown slowdowner:slowdowner /data
 USER slowdowner
 CMD yarn run start
-EXPOSE 8080
+EXPOSE 8080