feat: implement new shortcut: press Escape to exit editing mode

frontend/app_flowy/packages/appflowy_editor/lib/src/service/internal_key_event_handlers/exit_editing_mode_handler.dart

@@ -0,0 +1,7 @@
+import 'package:appflowy_editor/src/service/shortcut_event/shortcut_event_handler.dart';
+import 'package:flutter/material.dart';
+
+ShortcutEventHandler exitEditingModeEventHandler = (editorState, event) {
+  editorState.service.selectionService.clearSelection();
+  return KeyEventResult.handled;
+};

frontend/app_flowy/packages/appflowy_editor/lib/src/service/shortcut_event/built_in_shortcut_events.dart

@@ -4,6 +4,7 @@ import 'package:appflowy_editor/src/service/internal_key_event_handlers/arrow_ke
 import 'package:appflowy_editor/src/service/internal_key_event_handlers/backspace_handler.dart';
 import 'package:appflowy_editor/src/service/internal_key_event_handlers/copy_paste_handler.dart';
 import 'package:appflowy_editor/src/service/internal_key_event_handlers/enter_without_shift_in_text_node_handler.dart';
+import 'package:appflowy_editor/src/service/internal_key_event_handlers/exit_editing_mode_handler.dart';
 import 'package:appflowy_editor/src/service/internal_key_event_handlers/markdown_syntax_to_styled_text.dart';
 import 'package:appflowy_editor/src/service/internal_key_event_handlers/page_up_down_handler.dart';
 import 'package:appflowy_editor/src/service/internal_key_event_handlers/redo_undo_handler.dart';
@@ -276,6 +277,11 @@ List<ShortcutEvent> builtInShortcutEvents = [
     command: 'shift+parenthesis right',
     handler: markdownLinkOrImageHandler,
   ),
+  ShortcutEvent(
+    key: 'Exit editing mode',
+    command: 'escape',
+    handler: exitEditingModeEventHandler,
+  ),
   // https://github.com/flutter/flutter/issues/104944
   // Workaround: Using space editing on the web platform often results in errors,
   //  so adding a shortcut event to handle the space input instead of using the

frontend/app_flowy/packages/appflowy_editor/test/service/internal_key_event_handlers/exit_editing_mode_handler_test.dart

@@ -0,0 +1,50 @@
+import 'package:appflowy_editor/appflowy_editor.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import '../../infra/test_editor.dart';
+
+void main() async {
+  setUpAll(() {
+    TestWidgetsFlutterBinding.ensureInitialized();
+  });
+
+  group('exit_editing_mode_handler.dart', () {
+    testWidgets('Exit editing mode', (tester) async {
+      const text = 'Welcome to Appflowy 😁';
+      const lines = 3;
+      final editor = tester.editor;
+      for (var i = 0; i < lines; i++) {
+        editor.insertTextNode(text);
+      }
+      await editor.startTesting();
+
+      // collaspsed selection
+      await _testSelection(editor, Selection.single(path: [1], startOffset: 0));
+
+      // single selection
+      await _testSelection(
+        editor,
+        Selection.single(path: [1], startOffset: 0, endOffset: text.length),
+      );
+
+      // mutliple selection
+      await _testSelection(
+        editor,
+        Selection(
+          start: Position(path: [0], offset: 0),
+          end: Position(path: [2], offset: text.length),
+        ),
+      );
+    });
+
+    // Future<void> _testSelection()
+  });
+}
+
+Future<void> _testSelection(
+    EditorWidgetTester editor, Selection selection) async {
+  await editor.updateSelection(selection);
+  expect(editor.documentSelection, selection);
+  await editor.pressLogicKey(LogicalKeyboardKey.escape);
+  expect(editor.documentSelection, null);
+}