add wagtail-freezer to Static site generation (#187)

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

README.md

@@ -103,6 +103,7 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 
 - [Wagtail-bakery](https://github.com/moorinteractive/wagtail-bakery) - A set of helpers for baking your Django Wagtail site out as flat files.
 - [Wagtail-Netlify](https://github.com/tomdyson/wagtail-netlify) - Easilly publish your statically rendered Wagtail site to Netlify.
+- [wagtail-freezer](https://github.com/gasman/wagtail-freezer) - Generates static HTML sites from a Wagtail project.
 
 ### Settings management