fix: command of double tilde to strikethrough

Author: abichinger

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

@@ -282,7 +282,7 @@ List<ShortcutEvent> builtInShortcutEvents = [
   ),
   ShortcutEvent(
     key: 'Double tilde to strikethrough',
-    command: 'shift+tilde',
+    command: 'tilde,shift+tilde',
     handler: doubleTildeToStrikethrough,
   ),
   ShortcutEvent(