Add Wagtail EditorJS (#217)

* Add Wagtail EditorJS plugin

Author: Nigel2392

README.md

@@ -74,6 +74,7 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 - [Wagtail Medium Editor](https://github.com/dperetti/Django-wagtailmedium) - A customizable Medium Editor for Wagtail, with link anchors support.
 - [WagtailDraftail](https://github.com/springload/wagtaildraftail) – Draft.js editor for Wagtail, built upon [Draftail](https://github.com/springload/draftail) and [draftjs_exporter](https://github.com/springload/draftjs_exporter).
 - [wagtail-readinglevel](https://github.com/vixdigital/wagtail-readinglevel) – Wagtail plugin to determine the reading level of text input into a rich text field.
+- [Wagtail EditorJS](https://github.com/Nigel2392/wagtail_editorjs) - An [EditorJS](https://editorjs.io/) widget with great support for Wagtail's page, image and document choosers.
 
 ### Widgets