### 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 = get_abis();
	Vector<ABI> enabled_abis;
	for (int i = 0; i < abis.size(); ++i) {
		bool is_enabled = p_preset->get("architectures/" + abis[i].abi);
		if (is_enabled) {
			enabled_abis.push_back(abis[i]);
		}
	}
	return enabled_abis;
}
void EditorExportPlatformAndroid::get_preset_features(const Ref<EditorExportPreset> &p_preset, List<String> *r_features) const {
	r_features->push_back("etc2");
	Vector<ABI> abis = get_enabled_abis(p_preset);
	for (int i = 0; i < abis.size(); ++i) {
		r_features->push_back(abis[i].arch);
		r_features->push_back(abis[i].abi);
	}
}
void EditorExportPlatformAndroid::get_export_options(List<ExportOption> *r_options) {