add: solidity and foundry support

[gabr1sr]

This PR:

• adds support for Solidity (languages.solidity, https://soliditylang.org/) with package option. Default package is pkgs.solc from nixpkgs.
• adds support for Foundry (languages.solidity.foundry, https://book.getfoundry.sh/) with package option. Default package is foundry-bin from foundry.nix.

Trying out

If you want to try this out, you will need to change your devenv.yaml:

inputs:
  devenv:
    url: github:gabr1sr/devenv/new/modules/solidity?dir=src/modules
  foundry:
    url: github:shazow/foundry.nix
    inputs:
      nixpkgs:
        follows: nixpkgs

And change your devenv.nix:

{ ... }:
{
  languages.solidity = {
    enable = true;
    foundry.enable = true;
  };
}

Related to shazow/foundry.nix#34

[domenkozar]

Need to run pre-commit run -a