### 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
return run_icon;
}
String EditorExportPlatformAndroid::get_adb_path() {
	String exe_ext = "";
	if (OS::get_singleton()->get_name() == "Windows") {
		exe_ext = ".exe";
	}
	String sdk_path = EDITOR_GET("export/android/android_sdk_path");
	return sdk_path.path_join("platform-tools/adb" + exe_ext);
}
String EditorExportPlatformAndroid::get_apksigner_path(int p_target_sdk, bool p_check_executes) {
	if (p_target_sdk == -1) {
		p_target_sdk = DEFAULT_TARGET_SDK_VERSION;
	}
	String exe_ext = "";
	if (OS::get_singleton()->get_name() == "Windows") {
		exe_ext = ".bat";
	}
	String apksigner_command_name = "apksigner" + exe_ext;
	String sdk_path = EDITOR_GET("export/android/android_sdk_path");
	String apksigner_path = "";
	Error errn;