Restore placeholders before turbolinks caches

[julianrubisch]

If a page is turbolinks-cached, it will show it in a flash, then render the futurism helpers.

However, if cached, it would preferable to simply use the cached version and halt everything.

Cf https://github.com/turbolinks/turbolinks#detecting-when-a-preview-is-visible, http://www.modernmpa.com/turbolinks

[julianrubisch]

cf https://dev.to/adrienpoly/animations-with-turbolinks-and-stimulus-4862

Contrary to my statement above, I now think the futurism-element's state should be restored to loading before navigation, so the cached version displays the loading elements.