### 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
Vector<uint8_t> png_buffer;
	Error err = PNGDriverCommon::image_to_png(p_splash_image, png_buffer);
	if (err == OK) {
		p_data.resize(png_buffer.size());
		memcpy(p_data.ptrw(), png_buffer.ptr(), p_data.size());
	} else {
		String err_str = String("Failed to convert splash image to png.");
		WARN_PRINT(err_str.utf8().get_data());
	}
}
void EditorExportPlatformAndroid::_process_launcher_icons(const String &p_file_name, const Ref<Image> &p_source_image, int dimension, Vector<uint8_t> &p_data) {
	Ref<Image> working_image = p_source_image;
	if (p_source_image->get_width() != dimension || p_source_image->get_height() != dimension) {
		working_image = p_source_image->duplicate();
		working_image->resize(dimension, dimension, Image::Interpolation::INTERPOLATE_LANCZOS);
	}
	Vector<uint8_t> png_buffer;
	Error err = PNGDriverCommon::image_to_png(working_image, png_buffer);
	if (err == OK) {
		p_data.resize(png_buffer.size());
		memcpy(p_data.ptrw(), png_buffer.ptr(), p_data.size());
	} else {
		String err_str = String("Failed to convert resized icon (") + p_file_name + ") to png.";
		WARN_PRINT(err_str.utf8().get_data());
	}
}
String EditorExportPlatformAndroid::load_splash_refs(Ref<Image> &splash_image, Ref<Image> &splash_bg_color_image) {