[feat] show signal fn

[nank1ro]

The Show widget now takes a functions that returns a bool. You easily convert any type to bool, for example:

final count = createSignal(0);

@override
Widget build(BuildContext context) {
  return Show(
    when: () => count() > 5,
    builder: (context) => const Text('Count is greater than 5'),
    fallback: (context) => const Text('Count is lower than 6'),
  );
}

[codecov[bot]]

Codecov Report

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