chore: add missing toJson implementation

Author: incendial

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_late_keyword/avoid_late_keyword_rule.dart

@@ -32,6 +32,15 @@ class AvoidLateKeywordRule extends CommonRule {
           includes: readIncludes(config),
         );
 
+  @override
+  Map<String, Object?> toJson() {
+    final json = super.toJson();
+    json[_ConfigParser._allowInitializedConfig] = _allowInitialized;
+    json[_ConfigParser._ignoredTypesConfig] = _ignoredTypes.toList();
+
+    return json;
+  }
+
   @override
   Iterable<Issue> check(InternalResolvedUnitResult source) {
     final visitor = _Visitor(_allowInitialized, _ignoredTypes);