Adding an empty keycap for keyboard letters
Hi, thank you very much for the font, it's really nice.

I was thinking that it will be nice to add also a keycap background for each letter in the keyboard like this ones 

![image](https://user-images.githubusercontent.com/3449006/165491132-57c3466f-83a2-4e5d-a1a3-d40c34b596c8.png)

Is it something that can be done?

Thank you