Motivation for this change

The user @rbasso, who has been an active member in the exercism community a long time ago, and was the only maintainer of the exercism package has left GitHub as it seems. His profile is nearly empty and does not show a single GitHub contribution over the last year.

As I am still an active GitHub user, an active member of the exercism.io community and a nixOS user and provided last two version bumps of the package, I think it makes sense to set myself as package maintainer.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.