Motivation for this change

Add the following models:

da_core_news_lg, da_core_news_md, da_core_news_sm, de_core_news_lg, el_core_news_lg, es_core_news_lg, fr_core_news_lg, it_core_news_lg, it_core_news_md, lt_core_news_lg, lt_core_news_md, nb_core_news_lg, nb_core_news_md, nl_core_news_lg, nl_core_news_md, pl_core_news_lg, pl_core_news_md, pl_core_news_sm, pt_core_news_lg, pt_core_news_md, ro_core_news_sm, ro_core_news_md, ro_core_news_lg, zh_core_web_lg, zh_core_web_md, zh_core_web_sm

I also checked the licenses and fixed them where necessary.

Some extra notes:

• I had to add a derivation for pkuseg, which is used by the zh models. Unfortunately, it seems to be proprietary due to the included data.
• I haven't included the Japanese models yet. These require sudachipy, however, that is its own can of worms to package, since it likes it sets symlinks in its Python path during runtime to switch dictionaries. Maybe later...

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.