feat: start to implement RPC multiqueries

lib/providers/substrate_sdk.dart

@@ -93,7 +93,7 @@ class SubstrateSdk with ChangeNotifier {
     try {
       return await sdk.webView!.evalJavascript('api.query.$call');
     } catch (e) {
-      log.i("catched _getStorage error");
+      log.e("_getStorage error: $e");
       return Future(() {});
     }
   }
@@ -200,6 +200,16 @@ class SubstrateSdk with ChangeNotifier {
     return balanceRatio;
   }
 
+  Future getBalanceMulti(List addresses) async {
+    List stringifyAddresses = [];
+    for (var element in addresses) {
+      stringifyAddresses.add('"$element"');
+    }
+    final List balanceGlobal =
+        await _getStorage('system.account.multi($stringifyAddresses)');
+    log.d('debug multi: $balanceGlobal');
+  }
+
   Future<Map<String, double>> getBalance(String address) async {
     if (!nodeConnected) {
       return {

lib/screens/home.dart

@@ -118,6 +118,15 @@ class _HomeScreenState extends State<HomeScreen> {
       isTall = true;
       ratio = 1.125;
     }
+
+    //TODO: finish to implement multiqueries
+    
+    // final sub = Provider.of<SubstrateSdk>(context, listen: false);
+    // sub.getBalanceMulti([
+    //   '5CQ8T4qpbYJq7uVsxGPQ5q2df7x3Wa4aRY6HUWMBYjfLZhnn',
+    //   '5Dq8xjvkmbz7q4g2LbZgyExD26VSCutfEc6n4W4AfQeVHZqz'
+    // ]);
+
     return Scaffold(
         resizeToAvoidBottomInset: false,
         drawer: MainDrawer(isWalletsExists: isWalletsExists),

lib/widgets/payment_popup.dart

@@ -145,6 +145,7 @@ void paymentPopup(BuildContext context, String toAddress, String username) {
                       ),
                       const SizedBox(height: 10),
                       Consumer<SubstrateSdk>(builder: (context, sub, _) {
+                        // TODO: about keyboard dismiss issue, should try this: https://stackoverflow.com/a/76352647/8301867
                         return DropdownButton(
                           dropdownColor: const Color(0xffffeed1),
                           elevation: 12,