add configuration to use sparkjave-mysql sample with Docker Dev Environments feature (#257)

add configuration to use sparkjava-mysql sample with Docker Dev Environments feature

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

sparkjava-mysql/backend/Dockerfile

@@ -1,3 +1,5 @@
+# syntax=docker/dockerfile:1.4
+
 FROM --platform=$BUILDPLATFORM maven:3.8.5-eclipse-temurin-17 AS build
 WORKDIR /workdir/server
 COPY pom.xml /workdir/server/pom.xml
@@ -7,6 +9,21 @@ COPY src /workdir/server/src
 
 RUN mvn --batch-mode clean compile assembly:single
 
+FROM build 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 / /
+CMD ["java", "-jar", "target/app.jar" ]
+
 FROM eclipse-temurin:17-jre-focal
 ARG DEPENDENCY=/workdir/server/target
 EXPOSE 8080