asyncEffect side effect

[busslina]

Usually, calling to requestFocus in initState or in use.callonce doesn't work, so a workaround is to call it asynchronously.

Here, two side effect helpers:

void afterBuild(void Function() callback) =>
      use.callonce(() => Future.microtask(callback));

void asyncEffect(void Function() callback, void Function() dispose) =>
    use.effect(
      () {
        Future.microtask(callback);
        return dispose;
      },
      [],
    );

void onDispose(void Function() callback) => use.effect(
      () => callback,
      [],
    );

Usage examle:

final focusScopeNode = use.focusScopeNode();

    use.asyncEffect(
      focusScopeNode.requestFocus,
      focusScopeNode.dispose,
    );