Add PageProofer code snippet to websites via cms.

First:

composer require dynamic/silverstripe-pageproofer

Then:

http://yoursite.com/dev/build?flush=all

Add PageProofer Codes in the Site Settings admin:

The code is automagically added to the page if the code domain matches your current domain and the code is enabled (both in Page Proofer and the cms):

See the docs/en folder.