Context menu don´t work inside shadowDOM.

If you create a component that extends HTMLElement and use shadowDOM, the context menus wont appear.
How to reproduce:
1. Create a class that extends HTMLElement
2. Create a ShadowDOM via: this.attachShadow({mode: 'open'});
3. Create a svelt-jsoneditor inside this custom Element
4. Context menu don´t work.

If you keep everthing the same but don´t use shadowDOM it works as expected.