build: add mkdir command to Dockerfile

this added folder are going to store the uploaded book covers

Author: vianavitor-dev

Dockerfile

@@ -6,6 +6,7 @@ RUN mvn clean package -DskipTests
 
 FROM eclipse-temurin:21-jre-alpine-3.23
 WORKDIR /app
+RUN mkdir -p /app/uploads
 COPY --from=build /app/target/*.jar app.jar
 EXPOSE 8080
 ENTRYPOINT ["java", "-jar", "app.jar"]