Compatibility with paragraph_previewer

Problem/Motivation

The module Paragraph_previewer use a field widget that extend the class "ParagraphsWidget". When you want to use the "dialog_off_canvas" option , the dialog can be openend but the list of paragraph types is empty.

Steps to reproduce

1° first chose the field widget "Paragraphs Previewer & Paragraphs EXPERIMENTAL"
2° Activate the "Use off-canvas instead of modal dialog","Enable add in between buttons" , "add mode with modal"
3° Create a node and click on the "more" link
4° The dialog will open empty

Proposed resolution

Instead of testing the component type (which is paragraphs_previewer instead of paragraph) we can check the "Use off-canvas" setting directly from the component.