I have done it in the the same way. But when I am selecting the option edit as HTML and I put my HTML code into it and convert it to block. The HTML design gets break completely.
THank you.I had gone through that link.Basically I want to integrate the Gutenberg editor with the simple html page like with textarea, like we do with ckeditor <textarea class=”ckeditor” name=”editor1″></textarea> and this textarea becomes the ckeditor. so like wise I want to do it with Gutenberg editor. So is it possible??