Document our backport policy
It has long been our policy to backport security fixes about 3 releases but not to backport general bug fixes except in special cases. I cannot find anywhere that we've written this down, with the exception of the security policy at https://gitlab.com/gitlab-org/release-tools/blob/master/doc/security.md#backporting. It would be great to put this in our docs so we can point users and customers there when they have questions.