How to fix SirTrevor editor error?

Question

Code editor

Why is the result with json displayed in the text?
In textarea I write an example "My text"
Result

{"data":[{"type":"text","data":{"text":"
Мой текст
","format":"html"}}]}

<textarea class="js-st-instance"></textarea>

new SirTrevor.Editor({ el: $('.js-st-instance') });