message: add instructions for a multi-stage build dockerfile
diff: @@ -67,6 +67,13 @@ COPY .yarn ./.yarn
  COPY .yarnrc.yml ./
  ```
  +In a multi-stage `Dockerfile`, each stage that runs a `yarn` command will also need the Yarn 3 installation. For example, in the final stage you may need to add the following:
  +
  +```Dockerfile
  +COPY --from=build --chown=node:node /app/.yarn ./.yarn
  +COPY --from=build --chown=node:node /app/.yarnrc.yml ./
  +```
  +
  The `--production` flag to `yarn install` has been removed in Yarn 3, instead you need to use `yarn workspaces focus --all --production` to avoid installing development dependencies in your production deployment. A tradeoff of this is that `yarn workspaces focus` does not support the `--immutable` flag.
  ```Dockerfile
  