Recall stored state to show an accurate initial skeleton

[kumar303]

When displaying a skeleton for the very first time, there is no way to guess what the layout state will be (click See initial state in this example).

However, the first load of a repeat visit could use something like local storage to recall the last layout state and render an accurate skeleton.

This ticket is about adding support for showing skeletons based on stored data.

Privacy: let's consider the risk of storing a page layout in a potentially insecure way. Maybe this just means adding a warning to the docs.