### 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
store_image(launcher_icon.export_path, data);
}
void EditorExportPlatformAndroid::store_image(const String &export_path, const Vector<uint8_t> &data) {
	String img_path = export_path.insert(0, "res://android/build/");
	store_file_at_path(img_path, data);
}
void EditorExportPlatformAndroid::_copy_icons_to_gradle_project(const Ref<EditorExportPreset> &p_preset,
		const String &processed_splash_config_xml,
		const Ref<Image> &splash_image,
		const Ref<Image> &splash_bg_color_image,
		const Ref<Image> &main_image,
		const Ref<Image> &foreground,
		const Ref<Image> &background) {
	
	if (!processed_splash_config_xml.is_empty()) {
		print_verbose("Storing processed splash configuration: " + String("\n") + processed_splash_config_xml);
		store_string_at_path(SPLASH_CONFIG_PATH, processed_splash_config_xml);
	}
	
	if (splash_image.is_valid() && !splash_image->is_empty()) {
		print_verbose("Storing splash image in " + String(SPLASH_IMAGE_EXPORT_PATH));
		Vector<uint8_t> data;
		_load_image_data(splash_image, data);
		store_image(SPLASH_IMAGE_EXPORT_PATH, data);
	}
	
	if (splash_bg_color_image.is_valid() && !splash_bg_color_image->is_empty()) {
		print_verbose("Storing splash background image in " + String(SPLASH_BG_COLOR_PATH));