Add issue template for unreproducible packages
Add issue template for unreproducible packages

It's nice to be able to easily create an issue for an unreproducibility,
but my additional motivation for creating this issue template is that it
makes it easier for non-maintainers to create issues that are correctly
tagged '8.topic: reproducible builds'.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs