Replace details about initial setup with a link

This is not specific to Doctrine and can be learnt elsewhere.

source/contribute.rst

@@ -41,29 +41,11 @@ contributing back to a Doctrine project.
 Initial Setup
 -------------
 
--  Clone the project
--  Setup a `GitHub <https://github.com>`_ account.
--  Fork the repository of the project you want to contribute to. In this example
-   it will be `DBAL <https://github.com/doctrine/dbal>`_
--  Make the local repository aware of your fork.
-
-.. code-block:: console
-
-    $ git clone --origin doctrine [email protected]:doctrine/dbal.git
-
-At that point, you have a repository, and you should be able to start
-doing changes. Later on, if you end up with something you are satisfied
-with, you will need to be able to push your changes to your fork.
-
-Here is how you can make your local repository aware of your fork:
-
-.. code-block:: console
-
-    $ cd dbal
-    $ git remote add fork [email protected]:username/dbal.git
-
-You should now have two remotes: one called ``doctrine``, another called
-``fork``.
+We are assuming you have cloned the project, have a Github account, and
+have forked the project. If any of this sounds unfamiliar, please `learn
+about that
+<https://docs.github.com/en/get-started/quickstart/contributing-to-projects>`_
+first.
 
 Choosing the right branch
 -------------------------