feat: New settings design

lib/pages/settings_chat/settings_chat.dart

@@ -1,5 +1,11 @@
 import 'package:flutter/material.dart';
 
+import 'package:adaptive_dialog/adaptive_dialog.dart';
+import 'package:flutter_gen/gen_l10n/l10n.dart';
+
+import 'package:fluffychat/config/app_config.dart';
+import 'package:fluffychat/config/setting_keys.dart';
+import 'package:fluffychat/widgets/matrix.dart';
 import 'settings_chat_view.dart';
 
 class SettingsChat extends StatefulWidget {
@@ -10,6 +16,31 @@ class SettingsChat extends StatefulWidget {
 }
 
 class SettingsChatController extends State<SettingsChat> {
+  void setJitsiInstanceAction() async {
+    const prefix = 'https://';
+    final input = await showTextInputDialog(
+      useRootNavigator: false,
+      context: context,
+      title: L10n.of(context).editJitsiInstance,
+      okLabel: L10n.of(context).ok,
+      cancelLabel: L10n.of(context).cancel,
+      textFields: [
+        DialogTextField(
+          initialText: AppConfig.jitsiInstance.replaceFirst(prefix, ''),
+          prefixText: prefix,
+        ),
+      ],
+    );
+    if (input == null) return;
+    var jitsi = prefix + input.single;
+    if (!jitsi.endsWith('/')) {
+      jitsi += '/';
+    }
+    final matrix = Matrix.of(context);
+    await matrix.store.setItem(SettingKeys.jitsiInstance, jitsi);
+    AppConfig.jitsiInstance = jitsi;
+  }
+
   @override
   Widget build(BuildContext context) => SettingsChatView(this);
 }