Consider changing notes tab pane layout on desktop

[tnajdek]

I realized that not showing the editor is questionable: when you have a lot of notes and select one of the last notes the editor will pop up and hide the selected note in the list. I think the easiest way around this would be to permanently show the editor on desktops.

Once we show the editor permanently I think it would make sense to allow creation of new notes by simply starting to type in the editor.

Originally posted by @flachware in https://github.com/zotero/web-library/issues/219#issuecomment-529471181