Office.js API get selected shapes method for Excel

Hi There,

In the current version, we can get selected data in PowerPoint/Excel/Word using `Office.context.document.getSelectedDataAsync`. However, this method can only work for some specific types of data such as `Office.CoercionType`.

In Excel, `ShapeType` is a also important kind of data, I want to modify some selected shapes in slides. Maybe I missed some methods to get the selected shapes in Excel, I would be appreciated if you have any ideas about that. I believe this is also really needed for developers.

Thank you so much in advance!