feat: add new default shortcuts for exisiting handlers v1 (#1786)

* feat: add new default shortcuts v1

* refactor: remove unnecessary space

Author: MayurSMahajan

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

@@ -112,23 +112,23 @@ List<ShortcutEvent> builtInShortcutEvents = [
   ),
   ShortcutEvent(
     key: 'Cursor begin select',
-    command: 'meta+shift+arrow left',
-    windowsCommand: 'ctrl+shift+arrow left',
-    linuxCommand: 'ctrl+shift+arrow left',
+    command: 'meta+shift+arrow left,shift+home',
+    windowsCommand: 'ctrl+shift+arrow left,shift+home',
+    linuxCommand: 'ctrl+shift+arrow left,shift+home',
     handler: cursorBeginSelect,
   ),
   ShortcutEvent(
     key: 'Cursor end select',
-    command: 'meta+shift+arrow right',
-    windowsCommand: 'ctrl+shift+arrow right',
-    linuxCommand: 'ctrl+shift+arrow right',
+    command: 'meta+shift+arrow right,shift+end',
+    windowsCommand: 'ctrl+shift+arrow right,shift+end',
+    linuxCommand: 'ctrl+shift+arrow right,shift+end',
     handler: cursorEndSelect,
   ),
   ShortcutEvent(
     key: 'Redo',
-    command: 'meta+shift+z',
-    windowsCommand: 'ctrl+shift+z',
-    linuxCommand: 'ctrl+shift+z',
+    command: 'meta+shift+z,meta+y',
+    windowsCommand: 'ctrl+shift+z,ctrl+y',
+    linuxCommand: 'ctrl+shift+z,ctrl+y',
     handler: redoEventHandler,
   ),
   ShortcutEvent(