Ability to specify boilerplate template for iframe body html

[zachleat]

Would love to globally specify boilerplate templates to use in an iframe document.

Right now our iframe demos don’t contain crucial document content. For example, in one project we have a <div class="layout"> that adds crucial horizontal padding on the document. Omitting this from the iframe means that breakpoints won’t quite match how they’ll look in the real template.

I’d like to add a data-boilerplate="SOME_KEY_POINTING_TO_A_TEMPLATE" to the data-xrayhtml element.

The important differentiation that makes this different from just including the boilerplate manually in the raw HTML is that it would not show in the snippet markup in the xray plugin.