Add substitutor suggestion to nix flake

[fkz]

I'm not sure if we should add this. When using this flake, you will get a suggestion to add the resp binary cache.

[Toxaris]

What is the effect of accepting the suggestion? I guess the local nix will download from the cache that is filled by the github action?

[fkz]

Yes, if your user is authorized to do so. In a multi-user nix installation, you may not even have the right to do so, I'm getting this warning even after accepting:

$ nix run github:potsdam-pnp/pf2e-cards/nix-substitutor
warning: ignoring untrusted substituter 'https://potsdam-pnp.cachix.org', you are not a trusted user.
Run `man nix.conf` for more information on the `substituters` configuration option.

So I think you need to configure this as a trusted substitutor somewhere as well.

[Toxaris]

Yeah just run into the same. I decided to sudoedit /etc/nix/nix.conf and add myself into the trusted users list. Then I had to jump through some hoops to restart the nix daemon, probably because I'm a noob and don't know how to "just restart" it :(

But now it seems to work.