clean: docker network declaration and build of the evolution/api image

[AdsonCicilioti]

SH code to check existence of unnecessary docker network.

   external: true

It is only for using an existing main network.
Since the docker-compose*.yml files are already primarily responsible for provisioning the main application stack, it doesn't make sense to create the network in a task outside its scope.

This is just a small contribution from someone who has just arrived and is already impressed with this community!

The docker build command will be removed in future releases in favor of buildx.
The Dockerfile build can be done by docker-compose*.yml itself by adding the build: . property in the api service.

[AdsonCicilioti]

@DavidsonGomes if the instruction to use the ./docker.sh file exists somewhere in the documentation, you will have to update to just use docker compose up -d.