Content Preloader Facebook Style

I am looking for an easy way to implement that content preloading animation when opening a website, so a user roughly knows what to expect such as this:

but somewhat feel it should work automatically while using the basic kirby tools given to us like when using kirbytext, outputting images etc.pp. without the need to define the size and view of each preloading box.

All examples I have seen also rather include only the view of a placeholder box, but not the actual way to replace the placeholder with the actual content when the page is fully loaded. I am looking forward to a neat way to integrate it with kirby.

Anyone ever did use something like that and give a few tipps?