Add a link to django-test-migrations

[sobolevn]

Hi, thanks a lot for building this example!

I am maintaining a similar project called django-test-migrations: https://github.com/wemake-services/django-test-migrations

Maybe you can add a link in the readme somewhere?

[alvassin]

Honestly, I didn’t plan to make a collection of links from this repository. But if someone asks about testing django migrations - I would be glad to mention your project.

Thank you for suggestion.