Make text field actions cumulative

[PavelHolec]

Actions that do not return value (such as shouldReturnKey) should be all able to be run in sequence to avoid passing the handler.

The technique works by reassigning the closure by also calling previous closure first:

extension EnvironmentValues {
  public var onSubmitAction: () -> Void {
    get {
      self[TriggerSubmitKey.self]
    } set {
      let oldValue = self[TriggerSubmitKey.self]
      self[TriggerSubmitKey.self] = {
        oldValue()
        newValue()
      }
    }
  }
}

Similar to native onSubmit that is cumulative and runs all provided handlers, not just the innermost one.

https://www.fivestars.blog/articles/onsubmit/