### Godot version

3.5.1.stable, v4.0.beta.custom_build [0a87ead64]

### System information

Ubuntu 22.04.1

### Issue description

For example, if project has name "300spartans", we can't enter the "org.godotengine.300spartans" to "Unique Name" field. We get the error "Invalid package name: A digit cannot be the first character in a package segment". But , if we enter "org.godotengine.$genname", there will be no error message. When exporting, the name will be set as "org.godotengine.spartans" without "300" in beginning, but user will not be informed about it. I think, it is not very good. It may not be worth making changes to the source code, but mention it in the documentation.

### Steps to reproduce

See issue description.

### Minimal reproduction project

N/A
}
		
		_copy_icons_to_gradle_project(p_preset, processed_splash_config_xml, splash_image, splash_bg_color_image, main_image, foreground, background);
		
		_write_tmp_manifest(p_preset, p_give_internet, p_debug);
		
		_clear_assets_directory();
		_remove_copied_libs();
		if (!apk_expansion) {
			print_verbose("Exporting project files...");
			CustomExportData user_data;
			user_data.assets_directory = assets_directory;
			user_data.debug = p_debug;
			err = export_project_files(p_preset, p_debug, rename_and_store_file_in_gradle_project, &user_data, copy_gradle_so);
			if (err != OK) {
				add_message(EXPORT_MESSAGE_ERROR, TTR("Export"), TTR("Could not export project files to gradle project."));
				return err;
			}
			if (user_data.libs.size() > 0) {
				Ref<FileAccess> fa = FileAccess::open(GDEXTENSION_LIBS_PATH, FileAccess::WRITE);
				fa->store_string(JSON::stringify(user_data.libs, "\t"));
			}
		} else {
			print_verbose("Saving apk expansion file...");
			err = save_apk_expansion_file(p_preset, p_debug, p_path);
			if (err != OK) {
				add_message(EXPORT_MESSAGE_ERROR, TTR("Export"), TTR("Could not write expansion package file!"));
				return err;
			}
		}