maintainers: create sage team

Maintaining all the packages whose updates might break some aspect of
sage.

For reference:
https://github.com/NixOS/nixpkgs/pull/103810#issuecomment-727536510

pkgs/development/libraries/gf2x/default.nix

@@ -32,7 +32,7 @@ stdenv.mkDerivation rec {
     description = ''Routines for fast arithmetic in GF(2)[x]'';
     homepage = "http://gf2x.gforge.inria.fr";
     license = licenses.gpl2Plus;
-    maintainers = with maintainers; [ raskin timokau ];
+    maintainers = with maintainers; [ raskin ] ++ teams.sage.members;
     platforms = platforms.unix;
   };
 }