"input" example allows line breaks in phone number

[psychon]

Hi there,

I was looking around how to have a number-only input field in ftxui 5.0.0 and came across the input example:

FTXUI/examples/component/input.cpp

Lines 34 to 41 in 5a9ef87

	// We are using `CatchEvent` to filter out non-digit characters.
	Component input_phone_number = Input(&phoneNumber, "phone number");
	input_phone_number |= CatchEvent([&](Event event) {
	return event.is_character() && !std::isdigit(event.character()[0]);
	});
	input_phone_number |= CatchEvent([&](Event event) {
	return event.is_character() && phoneNumber.size() > 10;
	});

While playing around with this example, I noticed that the "Return" key is allowed to add line breaks to the telephone number. That does not feel like it is intended.

(For my own use I got rid of this by having multiline = false in the options of the input component, see

FTXUI/src/ftxui/component/input.cpp

Lines 346 to 349 in 5a9ef87

	bool HandleReturn() {
	if (multiline()) {
	HandleCharacter("\n");
	}

[HiperDoo]

I also noticed this problem, by default it is in multiline mode (in my case it is totally inconvenient since I have many cells where parameters are filled with keywords).

But there is a simple solution without the need to edit the source code:

ftxui::InputOption input_option() {
      ftxui::InputOption option{ftxui::InputOption::Default()};
      option.multiline = false;
      return option;
  }

std::string name = "Name Example";
ftxui::Component input_field{ftxui::Input(&name, name, input_option())};