add articles for upgrading to Wagtail 3.0 (#190)

Co-authored-by: LB Johnston <lb.johnston@virginaustralia.com>

README.md

@@ -252,6 +252,8 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 - [Drupal Front End WTF, Wagtail Front End FTW](https://medium.com/@kevinhowbrook/drupal-front-end-wtf-wagtail-front-end-ftw-17712628df3e) - Comparing Drupal and Wagtail Markup and approach to each CMS
 - [How to Create and Manage Menus of Wagtail application](https://www.accordbox.com/blog/wagtail-tutorial-12-how-create-and-manage-menus-wagtail-application/)
 - [PythonEatsTail](https://pythoneatstail.com) - Complete written and video tutorials to create a Wagtail site with multiple languages, authentication and more
+- [Upgrading to Wagtail 3.0](https://enzedonline.com/en/tech-blog/upgrading-to-wagtail-3-0/) - General tips to migrate your codebase to Wagtail 3.0.
+- [Upgrading to Wagtail 3.0 Part 1](https://cynthiakiser.com/blog/2022/06/01/wagtail-3-upgrade-part-1.html) & [Upgrading to Wagtail 3.0 Part 2](https://cynthiakiser.com/blog/2022/06/02/wagtail-3-upgrade-part-2.html) - Two part series in how to migrate to Wagtail 3.0 with specific code examples.
 
 ### Recipes