Add Wagtail Yoast (#151)

Co-authored-by: Alexis LE BARON <contact@alexis-le-baron.com>

README.md

@@ -120,6 +120,7 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 - [wagtail-opengraph-image-generator](https://github.com/candylabshq/wagtail-opengraph-image-generator) - Assists you in automatically creating Open Graph images for your Wagtail pages.
 - [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.
 
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