added loading indicators to charts.

lib/pages/analytics/widgets/charts_loading_widget.dart

@@ -0,0 +1,24 @@
+import 'package:flutter/material.dart';
+
+class ChartsLoadingWidget extends StatelessWidget {
+  const ChartsLoadingWidget({
+    required this.isLoading,
+    super.key,
+  });
+  final bool isLoading;
+
+  @override
+  Widget build(BuildContext context) {
+    return Visibility(
+      visible: isLoading,
+      child: const SizedBox.square(
+        dimension: 16,
+        child: FittedBox(
+          child: CircularProgressIndicator(
+            padding: EdgeInsetsDirectional.only(end: 8),
+          ),
+        ),
+      ),
+    );
+  }
+}