### 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
r_options->push_back(ExportOption(PropertyInfo(Variant::BOOL, vformat("%s/%s", PNAME("permissions"), String(*perms).to_lower())), false));
		perms++;
	}
}
String EditorExportPlatformAndroid::get_name() const {
	return "Android";
}
String EditorExportPlatformAndroid::get_os_name() const {
	return "Android";
}
Ref<Texture2D> EditorExportPlatformAndroid::get_logo() const {
	return logo;
}
bool EditorExportPlatformAndroid::should_update_export_options() {
	bool export_options_changed = plugins_changed.is_set();
	if (export_options_changed) {
		
		plugins_changed.clear();
	}
	return export_options_changed;
}
bool EditorExportPlatformAndroid::poll_export() {
	bool dc = devices_changed.is_set();
	if (dc) {
		
		devices_changed.clear();
	}
	return dc;
}
int EditorExportPlatformAndroid::get_options_count() const {