nixos/firefox: detail the format of preferences (#260204)

        Some of these might be able to be configured more ergonomically

        using policies.

        See [here](https://mozilla.github.io/policy-templates/#preferences) for allowed preferences.

        ${organisationInfo}

      '';

      example = lib.literalExpression ''

        {

          "browser.tabs.tabmanager.enabled" = false;

        }

      '';

    };

    preferencesStatus = lib.mkOption {