This is a Mix project setup to build a Release named app using the official
Dockerfile.
You can customize the build step with app/bin/build and the run step with
app/bin/run.
Both of these are copied into the final release directory using an overlay
config in app/mix.exs
The Dockerfile copies the everything commited within the /app directory
and runs the app/bin/build script.
Depending on your .gitignore settings, you can include the deps/ directory
for any compilation of third party libraries.
You should not include the app/_build directory.