feat(zfs): declare ZFS module

modules/zfs/default.nix

@@ -0,0 +1,15 @@
+{ lib, config, ... }:
+
+{
+  options.zfs.enable = lib.mkOption {
+    default = false;
+    type = lib.types.bool;
+  };
+
+  config = lib.mkIf config.zfs.enable {
+    boot = {
+      kernelParams = [ "zfs.zfs_arc_max=12884901888" ];
+      zfs.forceImportRoot = lib.mkDefault false;
+    };
+  };
+}