### 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
zip_fileinfo fileinfo = get_zip_fileinfo();
		zipOpenNewFileInZip2(final_apk,
				file.utf8().get_data(),
				&fileinfo,
				extra,
				info.size_file_extra + padding,
				nullptr,
				0,
				nullptr,
				method,
				level,
				1); 
		zipWriteInFileInZip(final_apk, data.ptr(), data.size());
		zipCloseFileInZipRaw(final_apk, info.uncompressed_size, info.crc);
		bias += padding;
		ret = unzGoToNextFile(tmp_unaligned);
	}
	zipClose(final_apk, nullptr);
	unzClose(tmp_unaligned);
	if (should_sign) {
		
		
		err = sign_apk(p_preset, p_debug, p_path, ep);
		if (err != OK) {
			CLEANUP_AND_RETURN(err);
		}
	}
	CLEANUP_AND_RETURN(OK);
}
void EditorExportPlatformAndroid::get_platform_features(List<String> *r_features) const {