Add: Microsoft Excel Light Theme

[Arenukvern]

• [ ] add Theme with Excel colors

old ideas

• [ ] Add: scss modifcatior --is-excel-default-color
• [ ] Add: logic to change themes - after vue 3 refactoring Idea: color of background must be the same as excel background color of cards - white

See old mock-up for color scheme: https://www.figma.com/file/Bzbcf8P4FCvR7YPdLTrRefJf/Sheets-Manager?node-id=0%3A1