add configuration to use react-express-mysql sample with Docker Dev Environments feature (#270)

Signed-off-by: Guillaume Lours <guillaume.lours@docker.com>

react-express-mysql/backend/Dockerfile

@@ -1,5 +1,7 @@
+# syntax=docker/dockerfile:1.4
+
 # if you're doing anything beyond your local machine, please pin this to a specific version at https://hub.docker.com/_/node/
-FROM node:lts
+FROM node:lts AS development
 
 # set our node environment, either development or production
 # defaults to production, compose overrides this to development on build and run
@@ -29,3 +31,17 @@ COPY . /code
 # using node here is still more graceful stopping then npm with --init afaik
 # I still can't come up with a good production way to run with npm and graceful shutdown
 CMD [ "node", "src/index.js" ]
+
+FROM development as dev-envs
+RUN <<EOF
+apt-get update
+apt-get install -y --no-install-recommends git
+EOF
+
+RUN <<EOF
+useradd -s /bin/bash -m vscode
+groupadd docker
+usermod -aG docker vscode
+EOF
+# install Docker tools (cli, buildx, compose)
+COPY --from=gloursdocker/docker / /