How to read "light DOM" content in lit-element?

[ami...@gmail.com]

I want to create a component `markdown-slides` which depends on it's innerHTML,

is there a way to read "light DOM" content in lit-element just like the `value` of `textarea`?

or, can I bind `innerHTML` in main DOM tree to a property?

The use case could be:

```

<markdown-slides>

# Hello

---

## Page 2

---

# The End

</markdown-slides>

```