Include acf-json directory in this repo

[jasonbahl]

When following the instructions in the README to develop against this site, it will only work if you point the .env vars to a site with all the expected post types, etc.

Since we're using ACF to define Post Types, Taxonomies and field groups, we could sync the acf-json to a directory in this repo and commit the field groups here.

That would help for folks looking to setup this site locally and experiment, and would also serve as good docs. Would also ensure our ACF Field Groups stay versioned controlled, which I'm embarrassed to say they are not at the moment.