backwards: Add 7zip

hosts/backwards/home.nix

@@ -13,7 +13,10 @@
         home.username = "alex";
         home.homeDirectory = "/home/alex";
 
-        home.packages = [ pkgs.vim ];
+        home.packages = [
+          pkgs.vim
+          pkgs.p7zip
+        ];
 
         home.stateVersion = "24.05";
       };