Add some popular packages (#205). Fix #200

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

README.md

@@ -126,6 +126,7 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 - [wagtail-redirect-importer](https://github.com/Frojd/wagtail-redirect-importer) - Your friendly neighborhood importer that lets you import redirects from different tabular data formats, such as .csv and .xls 
 - [wagtail-meta-preview](https://github.com/rinti/wagtail-meta-preview) - Adds ability to get share previews for Facebook, Twitter and Google in the Wagtail admin.
 - [Wagtail Yoast](https://github.com/Aleksi44/wagtailyoast) - A tool to improve readability of your texts with SEO recommendations.
+- [Wagtail SEO](https://github.com/coderedcorp/wagtail-seo) - Search engine and social media optimization for Wagtail.
 
 ### Analytics
 
@@ -185,6 +186,7 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 
 - [wagtail-admin-list-controls](https://github.com/ixc/wagtail-admin-list-controls) - Adds advanced search, ordering and layout controls to Wagtail's modeladmin list views.
 - [wagtail-rangefilter](https://github.com/wunderweiss/wagtail-rangefilter) - Integrates django-admin-rangefilter into Wagtail's ModelAdmin.
+- [wagtail-treemodeladmin](https://github.com/cfpb/wagtail-treemodeladmin) - Page explorer-like navigation of Django model relationships using ModelAdmin.
 
 ### Misc
 
@@ -211,6 +213,7 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 - [Wagtail Grapple](https://github.com/torchbox/wagtail-grapple) - A Wagtail app that makes building GraphQL endpoints a breeze.
 - [Wagtail Secret Sharing](https://github.com/vicktornl/wagtail-secret-sharing) - Keep sensitive information out of your chat logs and email via a secure sharing protocol
 - [Wagtail Cache Invalidator](https://github.com/vicktornl/wagtail-cache-invalidator) - Invalidate and purge (frontend) cache via an user-friendly interface in the Wagtail CMS.
+- [Wagtail Headless Preview](https://github.com/torchbox/wagtail-headless-preview) -  Previews for headless Wagtail setups
 
 ## Tools