🐳️ multistage: remove devDependencies (#5477)

Docker Multistage
* Remove `devDependencies` from `./node_modules`
 in `builder` for faster copy on `base` init

* Added `isomorphic-unfetch` to show it not
 being copied over to `base`.

* `isomorphic-fetch` will still show from `next`

examples/with-docker/Dockerfile.multistage

@@ -4,7 +4,7 @@ WORKDIR /app
 COPY package.json .
 RUN yarn install
 COPY . .
-RUN yarn build
+RUN yarn build && yarn --production
 
 # And then copy over node_modules, etc from that stage to the smaller base image
 FROM mhart/alpine-node:base

examples/with-docker/package.json

@@ -11,5 +11,8 @@
     "react": "16.2.0",
     "react-dom": "16.2.0"
   },
+  "devDependencies": {
+    "isomorphic-unfetch": "^3.0.0"
+  },
   "license": "ISC"
 }