Improve layout when loading note view on touch

[tnajdek]

What I can see there are more issues left than the hidden spinner, primarily the layout being unstable during reload: when you reload, the touch-header in the item-details disappears for a moment and during this time the note does not fill the entire height.

Originally posted by @flachware in https://github.com/zotero/web-library/issues/321#issuecomment-557494728