reduce docker layer size

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Added
 ### Changed
+
+- minify containers to reduce layer size
+
 ### Fixed
 
 - do not show login note if it is not set

Dockerfile

@@ -3,11 +3,22 @@ MAINTAINER OhMyForm <admin@ohmyform.com>
 
 WORKDIR /usr/src/app
 
+RUN apk update && apk add curl bash && rm -rf /var/cache/apk/*
+
+# install node-prune (https://github.com/tj/node-prune)
+RUN curl -sfL https://install.goreleaser.com/github.com/tj/node-prune.sh | bash -s -- -b /usr/local/bin
+
 COPY . ./
 
 RUN yarn install --frozen-lock-file
 RUN yarn build
 
+# remove development dependencies
+RUN npm prune --production
+
+# run node prune
+RUN /usr/local/bin/node-prune
+
 FROM node:12-alpine
 MAINTAINER OhMyForm <admin@ohmyform.com>