feat: overall UI rework in Settings View (#53)

lib/ui/widgets/shared/custom_sliver_app_bar.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+import 'package:revanced_manager/theme.dart';
+
+class CustomSliverAppBar extends StatelessWidget {
+  final Widget title;
+  final PreferredSizeWidget? bottom;
+
+  const CustomSliverAppBar({
+    Key? key,
+    required this.title,
+    this.bottom,
+  }) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return SliverAppBar(
+      pinned: true,
+      snap: false,
+      floating: false,
+      expandedHeight: 100.0,
+      automaticallyImplyLeading: false,
+      backgroundColor: MaterialStateColor.resolveWith(
+        (states) => states.contains(MaterialState.scrolledUnder)
+            ? isDark
+                ? Theme.of(context).colorScheme.primary
+                : Theme.of(context).navigationBarTheme.backgroundColor!
+            : Theme.of(context).scaffoldBackgroundColor,
+      ),
+      flexibleSpace: FlexibleSpaceBar(
+        titlePadding: const EdgeInsets.symmetric(
+          vertical: 23.0,
+          horizontal: 20.0,
+        ),
+        title: title,
+      ),
+      bottom: bottom,
+    );
+  }
+}