Improving entrypoint.sh to run services in foreground

[rafaelstz]

WHY are these changes introduced?

Running Docker on Heroku or locally with the previous entrypoint.sh we cannot access the container's terminal since it's not running the services in the foreground.

WHAT is this pull request doing?

I'm running php-fpm and nginx in the background, allowing easy access to the container's terminal when using Heroku or the local environment.

In a Docker environment, it's better to avoid using init systems like OpenRC and instead to start the main process of the container (in this case, nginx or php-fpm) directly in the foreground. That's why it's more common to see nginx -g 'daemon off;' or php-fpm as the command to start the container. This is because Docker itself takes over many of the roles of an init system.

Checklist

Note: once this PR is merged, it becomes a new release for this template.

• I have added/updated tests for this change
• I have made changes to the README.md file and other related documentation, if applicable