Add REST API - Head Tags plugin in documentation

[juanmaguitar]

https://wordpress.org/plugins/rest-api-head-tags/

https://community.frontity.org/t/rest-api-head-tags-plugin-breaking-with-password-protected/1071

[mburridge]

We already have this page in the docs: https://docs.frontity.org/frontity-plugins/rest-api-head-tags

[juanmaguitar]

Recommend this plugins in the Architecture page
https://wordpress.org/plugins/headless-mode/