title: SwiftUI updating array state doesn't update view
body: <p>Here is my test code:</p>
  
  <pre><code>struct ArrView: View {
      @State var arr: [String] = ["first", "second"]
      var body: some View {
          VStack {
              Button("append") {self.arr.append("item\(self.arr.count)")}
              List(arr.indices) {row in
                  Text(self.arr[row])
              }
          }
      }
  }
  </code></pre>
  
  <p>When the 'append' Button was pressed, the <code>List</code> view didn't update.
  Am I doing wrong?</p>