Add support for render.com

[Ivaylo-Bachvarov]

Context

Add a render.yml in order to support easy deploying on https://render.com/.

The configuration contains 3 worker types.

1. Web worker
2. Celery background worker
3. Celery beats to schedule tasks

It also includes a PostgreSQL database, a reddis that is used as a queue and a var group to share environment variables for all the 3 services.