docs(docker-build): Update readme

packages/docker-build/README.md

@@ -9,3 +9,57 @@ Install the latest plugin.
 ```sh
 yarn plugin import https://github.com/Dcard/yarn-plugins/releases/latest/download/plugin-docker-build.js
 ```
+
+## Dockerfile
+
+The following is a basic example of `Dockerfile`.
+
+```dockerfile
+FROM node:12-alpine AS builder
+
+# Install dependencies for building native libraries
+RUN apk add --update git openssh-client python make gcc g++
+
+WORKDIR /workspace
+
+# docker-build plugin copies everything needed for `yarn install` to `manifests` folder.
+COPY manifests ./
+
+RUN yarn install --immutable
+
+# You can delete the cache folder after `yarn install` is done.
+RUN rm -rf .yarn/cache
+
+FROM node:12-alpine
+
+WORKDIR /workspace
+
+# Copy the installed dependencies from the previous stage.
+COPY --from=builder /workspace ./
+
+# docker-build plugin runs `yarn pack` in all workspace dependencies and copies them to `packs` folder.
+COPY packs ./
+
+CMD yarn workspace @foo/bar start
+```
+
+## CLI
+
+### `yarn docker build`
+
+This command will build a efficient Docker image which only contains production dependencies for the specified workspace.
+
+You have to create a `Dockerfile` in your workspace or your project. You can also specify the path to Dockerfile using the `-f, --file` option.
+
+Additional arguments can be passed to `docker build` directly, please check the Docker docs for more info: https://docs.docker.com/engine/reference/commandline/build/
+
+Example:
+
+```sh
+yarn docker build @foo/bar
+yarn docker build @foo/bar -t image-tag
+```
+
+#### `-f,--file`
+
+Path to `Dockerfile`. Default to the Dockerfile in the workspace or the project.