Add copy with to modlist

lib/mod_list.dart

@@ -501,6 +501,21 @@ class ModList {
     }
     return generateLoadOrder();
   }
+
+  ModList copyWith({
+    String? configPath,
+    String? modsPath,
+    Map<String, Mod>? mods,
+    Map<String, bool>? activeMods,
+  }) {
+    final newModlist = ModList(
+      configPath: configPath ?? this.configPath,
+      modsPath: modsPath ?? this.modsPath,
+    );
+    newModlist.mods = mods ?? this.mods;
+    newModlist.activeMods = activeMods ?? this.activeMods;
+    return newModlist;
+  }
 }
 
 String _expansionNameFromId(String id) {