Added a more prominent donations section. (#5092)

* Added a more prominent donations section.

Since we want more people to help sustain the project, let's make the donation section more prominent.

* Added the same section to the documentation's main page.

README.rst

@@ -9,8 +9,21 @@
 :Keywords: task, queue, job, async, rabbitmq, amqp, redis,
   python, distributed, actors
 
+Donations
+=========
+
+This project relies on your generous donations.
+
+If you are using Celery to create a commercial product, please consider becoming our `backer`_ or our `sponsor`_ to ensure Celery's future.
+We also offer priority support for those who will become our **`Silver`_** or **`Gold`_** sponsors.
+
+.. _`backer`: https://opencollective.com/celery#backer
+.. _`sponsor`: https://opencollective.com/celery#sponsor
+.. _`Silver`: https://opencollective.com/celery/order/5153
+.. _`Gold`: https://opencollective.com/celery/order/5152
+
 Sponsors
-========
+--------
 
 |ImageLink|_
 

docs/index.rst

@@ -15,6 +15,19 @@ or :ref:`our mailing-list <mailing-list>`.
 
 Celery is Open Source and licensed under the `BSD License`_.
 
+Donations
+=========
+
+This project relies on your generous donations.
+
+If you are using Celery to create a commercial product, please consider becoming our `backer`_ or our `sponsor`_ to ensure Celery's future.
+We also offer priority support for those who will become our **`Silver`_** or **`Gold`_** sponsors.
+
+.. _`backer`: https://opencollective.com/celery#backer
+.. _`sponsor`: https://opencollective.com/celery#sponsor
+.. _`Silver`: https://opencollective.com/celery/order/5153
+.. _`Gold`: https://opencollective.com/celery/order/5152
+
 Getting Started
 ===============