Floating rect selection disappears on blur #411

First, thank you for creating this component. Amazing work! I know how complicated this is, and I appreciate your work here. It saved me tons of time.

Regarding the issue, when you click anywhere else, the selection rectangle (.Spreadsheet__floating-rect) disappears. This makes sense most of the time, but if you click on a different window, the selection still disappears.

This is an issue because you may highlight some cells that you want to focus on and if you're writing a document in another window, as soon as you click on the document, the selection disappears.

The same issue occurs if you build a page with the spreadsheet on one side and something related on the other. You make a selection on one side and do something with it on the other. But currently, you can't do this because as soon as you click anywhere, even if it's on a completely separate component, the selection will disappear.