add warning text to the seed screen (#587)

* Add warning text to the seed screen

* fix font size

lib/src/screens/wallet_keys/wallet_keys_page.dart

@@ -1,3 +1,4 @@
+import 'package:auto_size_text/auto_size_text.dart';
 import 'package:cake_wallet/utils/show_bar.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/cupertino.dart';
@@ -18,7 +19,36 @@ class WalletKeysPage extends BasePage {
 
   @override
   Widget body(BuildContext context) {
-    return Container(
+    return Column(
+        children: [
+          Expanded(
+            child: Padding(
+              padding: const EdgeInsets.symmetric(horizontal: 24.0),
+              child: Container(
+                width: double.infinity,
+                decoration: BoxDecoration(
+                    borderRadius: BorderRadius.circular(12.0),
+                  color: Theme.of(context).accentTextTheme!.caption!.color!,
+                ),
+                child: Center(
+                  child: Padding(
+                    padding: const EdgeInsets.all(8.0),
+                    child: AutoSizeText(
+                        S.of(context).do_not_share_warning_text.toUpperCase(),
+                        textAlign: TextAlign.center,
+                        maxLines: 4,
+                        style: TextStyle(
+                          fontSize: 16,
+                            fontWeight: FontWeight.w500,
+                            color: Colors.red)),
+                  ),
+                ),
+              ),
+            ),
+          ),
+          Expanded(
+            flex: 7,
+          child: Container(
         padding: EdgeInsets.only(top: 20.0, bottom: 20.0),
         child: Observer(
           builder: (_) {
@@ -48,6 +78,6 @@ class WalletKeysPage extends BasePage {
                   );
                 });
           },
-        ));
+        )))]);
   }
 }