### 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<PluginConfigAndroid> enabled_plugins;
	Vector<PluginConfigAndroid> all_plugins = get_plugins();
	for (int i = 0; i < all_plugins.size(); i++) {
		PluginConfigAndroid plugin = all_plugins[i];
		bool enabled = p_presets->get("plugins/" + plugin.name);
		if (enabled) {
			enabled_plugins.push_back(plugin);
		}
	}
	return enabled_plugins;
}
Error EditorExportPlatformAndroid::store_in_apk(APKExportData *ed, const String &p_path, const Vector<uint8_t> &p_data, int compression_method) {
	zip_fileinfo zipfi = get_zip_fileinfo();
	zipOpenNewFileInZip(ed->apk,
			p_path.utf8().get_data(),
			&zipfi,
			nullptr,
			0,
			nullptr,
			0,
			nullptr,
			compression_method,
			Z_DEFAULT_COMPRESSION);
	zipWriteInFileInZip(ed->apk, p_data.ptr(), p_data.size());
	zipCloseFileInZip(ed->apk);
	return OK;
}
Error EditorExportPlatformAndroid::save_apk_so(void *p_userdata, const SharedObject &p_so) {