Installation of MC.js pixel

[ciaobeau]

In the ecommerce/stores endpoint there is now a nested object called connected_sites which provides a javascript snippet. This snippet needs to be installed on the user's ecommerce/site (loads on every page) so that MailChimp can insert javascript for features. The snippet url is located in the site__script / url field.

For more details, pls see this document: https://docs.google.com/document/d/126d81dXZ3GEGeCHg8b9m3DbXdlet-5sW0A50iobNRes/edit?usp=sharing