### 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
if (p_debug_flags & DEBUG_FLAG_REMOTE_DEBUG) {
				int dbg_port = EDITOR_GET("network/debug/remote_port");
				args.clear();
				args.push_back("-s");
				args.push_back(devices[p_device].id);
				args.push_back("reverse");
				args.push_back("tcp:" + itos(dbg_port));
				args.push_back("tcp:" + itos(dbg_port));
				output.clear();
				OS::get_singleton()->execute(adb, args, &output, &rv, true);
				print_verbose(output);
				print_line("Reverse result: " + itos(rv));
			}
			if (p_debug_flags & DEBUG_FLAG_DUMB_CLIENT) {
				int fs_port = EDITOR_GET("filesystem/file_server/port");
				args.clear();
				args.push_back("-s");
				args.push_back(devices[p_device].id);
				args.push_back("reverse");
				args.push_back("tcp:" + itos(fs_port));
				args.push_back("tcp:" + itos(fs_port));
				output.clear();
				err = OS::get_singleton()->execute(adb, args, &output, &rv, true);
				print_verbose(output);
				print_line("Reverse result2: " + itos(rv));
			}
		} else {
			static const char *const msg = "--- Device API < 21; debugging over Wi-Fi ---";
			EditorNode::get_singleton()->get_log()->add_message(msg, EditorLog::MSG_TYPE_EDITOR);
			print_line(String(msg).to_upper());