### 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
splash_image = Ref<Image>(memnew(Image(boot_splash_png)));
	}
	if (scale_splash) {
		Size2 screen_size = Size2(GLOBAL_GET("display/window/size/viewport_width"), GLOBAL_GET("display/window/size/viewport_height"));
		int width, height;
		if (screen_size.width > screen_size.height) {
			
			height = screen_size.height;
			width = splash_image->get_width() * screen_size.height / splash_image->get_height();
		} else {
			
			width = screen_size.width;
			height = splash_image->get_height() * screen_size.width / splash_image->get_width();
		}
		splash_image->resize(width, height);
	}
	
	bool bg_color_valid;
	Color bg_color = ProjectSettings::get_singleton()->get("application/boot_splash/bg_color", &bg_color_valid);
	if (!bg_color_valid) {
		bg_color = boot_splash_bg_color;
	}
	print_verbose("Creating splash background color image.");
	splash_bg_color_image.instantiate();
	splash_bg_color_image->initialize_data(splash_image->get_width(), splash_image->get_height(), false, splash_image->get_format());
	splash_bg_color_image->fill(bg_color);
	String processed_splash_config_xml = vformat(SPLASH_CONFIG_XML_CONTENT, bool_to_string(apply_filter));
	return processed_splash_config_xml;
}
void EditorExportPlatformAndroid::load_icon_refs(const Ref<EditorExportPreset> &p_preset, Ref<Image> &icon, Ref<Image> &foreground, Ref<Image> &background) {