Add a basic README.md in docker to explain how to use it

Author: pythys

docker/README.md

@@ -0,0 +1,19 @@
+# Moqui On Docker
+
+This directory contains everything needed to deploy moqui on docker. To do so
+follow these instructions:
+
+- Choose a docker compose file in `docker/`. For example to deploy moqui on
+  postgres you can choose moqui-postgres-compose.yml.
+- Find and download a suitable JDBC driver for the target database, download its
+  jar file and place it in `runtime/lib`.
+- Generate moqui war file `./gradlew build`
+- Get into docker folder `cd docker`
+- Build chosen compose file, e.g. `./build-compose-up.sh moqui-postgres-compose.yml`
+
+This last step would build the "moqui" image and deploy all services. You can
+confirm by accessing the system on http://localhost
+
+For a more secure and complete deployment, it is recommended to carefully review
+the compose files and adjust as needed, including changing credentials and other
+settings such as setting the host names, configuring for letsencrypt, etc ...