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/fflas-ffpack/default.nix

@@ -52,7 +52,7 @@ stdenv.mkDerivation rec {
     inherit version;
     description = ''Finite Field Linear Algebra Subroutines'';
     license = licenses.lgpl21Plus;
-    maintainers = with maintainers; [ raskin timokau ];
+    maintainers = with maintainers; [ raskin ] ++ teams.sage.members;
     platforms = platforms.unix;
     homepage = "https://linbox-team.github.io/fflas-ffpack/";
   };