add invite blocking support plus msc4494 support

To accomplish this I also reworked how account data is stored and added a method to fetch capabilities, and another method to set account data

lib/models/requests/set_account_data.dart

@@ -0,0 +1,15 @@
+import "package:freezed_annotation/freezed_annotation.dart";
+part "set_account_data.freezed.dart";
+part "set_account_data.g.dart";
+
+@freezed
+abstract class SetAccountDataRequest with _$SetAccountDataRequest {
+  const factory SetAccountDataRequest({
+    required String type,
+    required dynamic content,
+    String? roomId,
+  }) = _SetAccountDataRequest;
+
+  factory SetAccountDataRequest.fromJson(Map<String, Object?> json) =>
+      _$SetAccountDataRequestFromJson(json);
+}