SlickList `appendTo` prop doesn't work with Shadow DOM

[Geloosa]

appendTo which is a query selector string doesn't work in Shadow DOM, as there's no way to select an element inside it just by a string, but a call to shadow host element's shadowRoot is required: document.querySelector("shadowHostSelector").shadowRoot.querySelector("appendToSelector").

If appendTo could receive HTMLElement reference directly, it would solve the issue.

Here's a PR for that: #188