Added nodemon to Dockerfile & docker-compose

[guillecro]

• Now nodemon is installed inside the image so we can use it during dev.
• Now the app dir points to the host src files. So hot-reload is enabled!

Note: I think maybe we should change the port of keycloak cause its the same as traefik, am i right?

[guillecro]

Added in readme.md how you should start all the containers for testing. And also added traefik as a dependency of the app service.