feature: enanble custom TextSelectionControls

- add test

packages/fleather/test/widgets/editor_text_selection_controllers_test.dart

@@ -0,0 +1,89 @@
+import 'dart:math' as math;
+
+import 'package:fleather/fleather.dart';
+import 'package:fleather/src/widgets/editor_input_client_mixin.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import '../testing.dart';
+
+class MyTextSelectionHandle extends StatefulWidget {
+  final Size size;
+  const MyTextSelectionHandle(
+      {super.key, required this.size});
+
+  @override
+  State<StatefulWidget> createState() {
+    return MyTextSelectionHandleState();
+  }
+}
+
+class MyTextSelectionHandleState
+    extends State<MyTextSelectionHandle> {
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      width: widget.size.width,
+      height: widget.size.height,
+      color: Colors.red,
+    );
+  }
+}
+
+class MyTextSelectionControllers
+    extends MaterialTextSelectionControls {
+  final Size size;
+  MyTextSelectionControllers(this.size);
+
+  @override
+  Widget buildHandle(BuildContext context,
+      TextSelectionHandleType type, double textHeight,
+      [VoidCallback? onTap]) {
+    final Widget handle = MyTextSelectionHandle(
+      size: size,
+    );
+
+    return switch (type) {
+      TextSelectionHandleType.left => Transform.rotate(
+          angle: math.pi / 2.0,
+          child: handle), // points up-right
+      TextSelectionHandleType.right =>
+        handle, // points up-left
+      TextSelectionHandleType.collapsed => Transform.rotate(
+          angle: math.pi / 4.0, child: handle), // points up
+    };
+  }
+}
+
+void main() {
+  group('CustomTextSelectionControllers', () { 
+
+    testWidgets('set customTextSelectionControllers',
+        (tester) async { 
+      final document = ParchmentDocument.fromJson([
+        {'insert': 'some text\n'}
+      ]);
+      FleatherController controller =
+          FleatherController(document: document);
+      FocusNode focusNode = FocusNode();
+      final Size testSize = Size(230, 5);
+      final editor = MaterialApp(
+        home: FleatherEditor(
+            controller: controller,
+            focusNode: focusNode,
+            textSelectionControls:
+                MyTextSelectionControllers(testSize)),
+      ); 
+      await tester.pumpWidget(editor);
+      await tester.tap(find.byType(RawEditor).first);
+      await tester.pumpAndSettle();
+      expect(focusNode.hasFocus, isTrue);
+      tester.binding.scheduleWarmUpFrame();
+      final handleState =
+          tester.state(find.byType(MyTextSelectionHandle))
+              as MyTextSelectionHandleState;
+      expect(handleState.context.size, testSize);
+    });
+  });
+}