Documenting how fixtures can be moved from /src/DataFixures to a custom directory

[sebastianstucke87]

Doctrine fixtures can be loaded from any directory/file (https://www.doctrine-project.org/projects/doctrine-data-fixtures/en/latest/how-to/loading-fixtures.html#loading-fixtures).

But it is not clear on how to do this with the DoctrineBundle:

1. "How to Override Symfony's default Directory Structure"

   • https://symfony.com/doc/current/configuration/override_dir_structure.html
   • No word of fixtures

2. "How to Override any Part of a Bundle"

   • https://symfony.com/doc/current/bundles/override.html
   • No mentions of directories/fixtures

3. "DoctrineFixturesBundle" (this repository)

   • https://symfony.com/bundles/DoctrineFixturesBundle/current/index.html
   • No option/configuration mentioned to customize the "DataFixtures"-directory.

[derrabus]

Thank you for your PR. Please try to find a PR title that describes and summarizes what the PR is doing.

[greg0ire]

Thanks @sebastianstucke87 !