### 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<ABI> abis;
	abis.push_back(ABI("armeabi-v7a", "arm32"));
	abis.push_back(ABI("arm64-v8a", "arm64"));
	abis.push_back(ABI("x86", "x86_32"));
	abis.push_back(ABI("x86_64", "x86_64"));
	return abis;
}
Vector<String> EditorExportPlatformAndroid::list_gdap_files(const String &p_path) {
	Vector<String> dir_files;
	Ref<DirAccess> da = DirAccess::open(p_path);
	if (da.is_valid()) {
		da->list_dir_begin();
		while (true) {
			String file = da->get_next();
			if (file.is_empty()) {
				break;
			}
			if (da->current_is_dir() || da->current_is_hidden()) {
				continue;
			}
			if (file.ends_with(PluginConfigAndroid::PLUGIN_CONFIG_EXT)) {
				dir_files.push_back(file);
			}
		}
		da->list_dir_end();
	}
	return dir_files;
}
Vector<PluginConfigAndroid> EditorExportPlatformAndroid::get_plugins() {