Create getting_started.rst

[valberg]

Trying to clear up the confusion from #326

Rendered it looks like this:

[valberg]

@AmitPhulera What do you think?

[AmitPhulera]

This looks good @valberg 🎉
Thanks for adding these.

[tisdall]

I know this is copied from the celery docs, but I'm wondering if CELERY_CACHE_BACKEND = 'django-cache' is actually correct... It seems like you need to use CELERY_RESULT_BACKEND = 'django-cache' to tell it to use the cache backend defined in django-celery-results and then CELERY_CACHE_BACKEND to specify which cache to use.

Regardless of the above, it might be good to include the CELERY_RESULT_EXTENDED documentation here too: https://docs.celeryq.dev/en/stable/django/first-steps-with-django.html