Theme preview should inject script in footer template for Theming v2 Themes

[abdul]

The theme preview is injecting script.js in document_head template which was fine for theming_v1 based themes.

The theming_v2 themes will now have script.js at the end of the page. That means, people need to do some work to migrate their javascript to adopt to this new situation (script.js loads at the end), and test.

This must be fixed to make sure we can have similar (if not same) locally. The order of script matters a lot, and if it's not right it leads to issues.