Fixed:
- Error when pasting into empty sheet
- Potential error if using percentage formatter with more than just `int`, `float` and wrong type hint [250](https://github.com/ragardner/tksheet/issues/250)
- Only show the selection box outline while the mouse is dragged if the control key is down
- `index` and `header` `Span` parameters were not working with function `readonly()`
Added:
- Shift + arrowkey bindings for expanding/contracting a selection box
- Functions for getting cell properties (options) [249](https://github.com/ragardner/tksheet/issues/249)
- Ability to edit index in treeview mode, if the binding is enabled
Improved:
- Very slight performance boost to treeview insert, inserting rows when rows are hidden