add app dockerfile

Author: Leonardo Sarmiento

docker-compose-lab/app/Dockerfile

@@ -0,0 +1,14 @@
+# syntax=docker/dockerfile:1
+FROM ubuntu:22.04
+
+# install app dependencies
+RUN apt-get update && apt-get install -y python3 python3-pip
+RUN pip install flask==3.0.*
+
+# install app
+COPY app.py /
+
+# final configuration
+ENV FLASK_APP=app
+EXPOSE 8000
+CMD ["flask", "run", "--host", "0.0.0.0", "--port", "9000"]