docs: Add release process documentation
docs: Add release process documentation

A small doc describing the formal release process.

Fixes #382

Signed-off-by: Fabian Deutsch <de69c509e52dfe544d526a81279fe21e1252748c@fedoraproject.org>

stu-gott/kubevirt,stu-gott/kubevirt,kubevirt/kubevirt,fabiand/kubevirt,rmohr/kubevirt,stu-gott/kubevirt,fabiand/kubevirt,davidvossel/kubevirt,davidvossel/kubevirt,davidvossel/kubevirt,stu-gott/kubevirt,rmohr/kubevirt,kubevirt/kubevirt,kubevirt/kubevirt,davidvossel/kubevirt,admiyo/kubevirt,admiyo/kubevirt,kubevirt/kubevirt