* Added change_case command
* Added switch_to_uppercase and switch_to_lowercase
Renamed change_case to switch_case.
* Updated the Keymap section of the Book
* Use flat_map instead of map + flatten
* Fix switch_to_uppercase using to_lowercase
* Switched 'Alt-`' to uppercase and '`' to lowercase
Co-authored-by: Cor <prive@corpeters.nl>