docs: switch ObservedObject to StateObject (#343)

Author: cbaker6

ParseSwift.playground/Pages/17 - SwiftUI - Finding Objects.xcplaygroundpage/Contents.swift

@@ -72,7 +72,7 @@ extension GameScore {
 struct ContentView: View {
 
     //: A view model in SwiftUI
-    @ObservedObject var viewModel = GameScore.query("points" > 2)
+    @StateObject var viewModel = GameScore.query("points" > 2)
         .order([.descending("points")])
         .viewModel
     @State var name = ""

ParseSwift.playground/Pages/18 - SwiftUI - Finding Objects With Custom ViewModel.xcplaygroundpage/Contents.swift

@@ -102,7 +102,7 @@ class ViewModel: ObservableObject {
 struct ContentView: View {
 
     //: A view model in SwiftUI
-    @ObservedObject var viewModel = ViewModel()
+    @StateObject var viewModel = ViewModel()
 
     var body: some View {
         NavigationView {

ParseSwift.playground/Pages/19 - SwiftUI - LiveQuery.xcplaygroundpage/Contents.swift

@@ -69,7 +69,7 @@ var query = GameScore.query("points" < 11)
 struct ContentView: View {
 
     //: A LiveQuery subscription can be used as a view model in SwiftUI
-    @ObservedObject var subscription = query.subscribe!
+    @StateObject var subscription = query.subscribe!
 
     var body: some View {
         VStack {

README.md

@@ -120,7 +120,7 @@ let myQuery = GameScore.query("points" > 9)
 struct ContentView: View {
 
     //: A LiveQuery subscription can be used as a view model in SwiftUI
-    @ObservedObject var subscription = myQuery.subscribe!
+    @StateObject var subscription = myQuery.subscribe!
 
     var body: some View {
         VStack {