Can we add how to programmatically clear the editor to the README/Documentation?

I spent some time trying to find in the API a way to clear the contents of the editor programmatically. After a few keyword searches across the repo I found #728 where @maximedupre shows a method of clearing the content of the editor that could be used upon form submission (my use case)

> You could also clear your trix editor dynamically by loading an empty state:
>```
>trixEditorElement.editor.loadJSON(JSON.parse('{"document": []}'))
>```

Can we add this to the documentation under the heading [Inserting & Deleting Text](https://github.com/basecamp/trix#inserting-and-deleting-text)? I would think this is a common use case. I could open up a PR for this.

Start with the README section titled “Inserting & Deleting Text” and review the clearing approach referenced from issue #728. Add a concise example showing how to clear the editor programmatically for a form-submission use case. Done means the README documents this common operation under the requested heading.

Written by the indexing model from the issue text.