Added GitHub actions to build container images

Dockerfile

@@ -7,6 +7,21 @@ RUN mvn -ntp dependency:go-offline
 COPY src/ /tmp/hapi-fhir-jpaserver-starter/src/
 RUN mvn clean install -DskipTests
 
+FROM build-hapi AS build-distroless
+RUN mvn package spring-boot:repackage -Pboot
+RUN mkdir /app && \
+    cp /tmp/hapi-fhir-jpaserver-starter/target/ROOT.war /app/main.war
+
+FROM gcr.io/distroless/java-debian10:11 AS release-distroless
+COPY --chown=nonroot:nonroot --from=build-distroless /app /app
+EXPOSE 8080
+# 65532 is the nonroot user's uid
+# used here instead of the name to allow Kubernetes to easily detect that the container
+# is running as a non-root (uid != 0) user.
+USER 65532:65532
+WORKDIR /app
+CMD ["/app/main.war"]
+
 FROM tomcat:9.0.38-jdk11-openjdk-slim-buster
 
 RUN mkdir -p /data/hapi/lucenefiles && chmod 775 /data/hapi/lucenefiles