feat: add restic for backups

common/nixos/restic.nix

@@ -0,0 +1,14 @@
+{...}: {
+  services.restic.backups = {
+    backups = {
+      user = "gwg313";
+      repository = "/backups";
+      initialize = true;
+      passwordFile = "/home/gwg313/restic.txt";
+      paths = ["/home/gwg313/Projects" "/home/gwg313/Documents" "/home/gwg313/.local/share/password-store" "/home/gwg313/.local/share/buku"];
+      timerConfig = {
+        onCalendar = "saturday 23:00";
+      };
+    };
+  };
+}