### 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
String project_icon_path = GLOBAL_GET("application/config/icon");
	icon.instantiate();
	foreground.instantiate();
	background.instantiate();
	
	String path = static_cast<String>(p_preset->get(launcher_icon_option)).strip_edges();
	print_verbose("Loading regular icon from " + path);
	if (path.is_empty() || ImageLoader::load_image(path, icon) != OK) {
		print_verbose("- falling back to project icon: " + project_icon_path);
		ImageLoader::load_image(project_icon_path, icon);
	}
	
	path = static_cast<String>(p_preset->get(launcher_adaptive_icon_foreground_option)).strip_edges();
	print_verbose("Loading adaptive foreground icon from " + path);
	if (path.is_empty() || ImageLoader::load_image(path, foreground) != OK) {
		print_verbose("- falling back to using the regular icon");
		foreground = icon;
	}
	
	path = static_cast<String>(p_preset->get(launcher_adaptive_icon_background_option)).strip_edges();
	if (!path.is_empty()) {
		print_verbose("Loading adaptive background icon from " + path);
		ImageLoader::load_image(path, background);
	}
}
void EditorExportPlatformAndroid::store_image(const LauncherIcon launcher_icon, const Vector<uint8_t> &data) {