Add '_' suffix when duplicating

scenes/weebo_scene_save_name.c

@@ -26,6 +26,9 @@ void weebo_scene_save_name_on_enter(void* context) {
             weebo->text_store, sizeof(weebo->text_store), WEEBO_APP_FILE_PREFIX);
         file_name_empty = true;
     } else {
+        // Add "_" suffix to make name unique
+        weebo->file_name[strlen(weebo->file_name)] = '_';
+        weebo->file_name[strlen(weebo->file_name)] = '\0';
         weebo_text_store_set(weebo, weebo->file_name);
     }
     text_input_set_header_text(text_input, "Name the card");