docs: replace deprecated widgets to updates ones

README.md

@@ -32,7 +32,7 @@ backgroundColor | Flushbar background color. Will be ignored if [backgroundGradi
 leftBarIndicatorColor | If not null, shows a left vertical bar to better indicate the humor of the notification. It is not possible to use it with a [Form] and I do not recommend using it with [LinearProgressIndicator].
 boxShadows | The shadows generated by Flushbar. Leave it null if you don't want a shadow. You can use more than one if you feel the need. Check [this example](https://github.com/flutter/flutter/blob/main/packages/flutter/lib/src/material/shadows.dart)
 backgroundGradient | Flushbar background gradient. Makes [backgroundColor] be ignored.
-mainButton | Use if you need an action from the user. [FlatButton] is recommended here.
+mainButton | Use if you need an action from the user. [TextButton] is recommended here.
 onTap | A callback that registers the user's click anywhere. An alternative to [mainButton]
 duration | How long until Flushbar will hide itself (be dismissed). To make it indefinite, leave it null.
 isDismissible | Determines if the user can swipe or click the overlay (if [routeBlur] > 0) to dismiss. It is recommended that you set [duration] != null if this is false. If the user swipes to dismiss or clicks the overlay, no value will be returned.
@@ -132,7 +132,7 @@ Flushbar(
         Icons.check,
         color: Colors.greenAccent,
       ),
-      mainButton: FlatButton(
+      mainButton: TextButton(
         onPressed: () {},
         child: Text(
           "CLAP",
@@ -277,23 +277,22 @@ bool _wasButtonClicked;
             flush = Flushbar<bool>(
               title: "Hey Ninja",
               message: "Lorem Ipsum is simply dummy text of the printing and typesetting industry",
-              icon: Icon(
-                       Icons.info_outline,
-                       color: Colors.blue,),
-              mainButton: FlatButton(
-                             onPressed: () {
-                                 flush.dismiss(true); // result = true
-                               },
-                             child: Text(
-                               "ADD",
-                               style: TextStyle(color: Colors.amber),
-                             ),
-                           ),) // <bool> is the type of the result passed to dismiss() and collected by show().then((result){})
-              ..show(context).then((result) {
-                setState(() { // setState() is optional here
-                  _wasButtonClicked = result;
-                });
+              icon: Icon(Icons.info_outline, color: Colors.blue),
+              mainButton: TextButton(
+                onPressed: () {
+                  flush.dismiss(true); // result = true
+                },
+                child: Text(
+                  "ADD",
+                  style: TextStyle(color: Colors.amber),
+                )
+              )
+            ) // <bool> is the type of the result passed to dismiss() and collected by show().then((result){})
+            ..show(context).then((result) {
+              setState(() { // setState() is optional here
+                _wasButtonClicked = result;
               });
+            });
           },
         ),
       ),