Add undo/redo functionality #2591 (#2623)

* initial work - undo works except typed keys

* working but clunky code

* single letter and paste with no selection working

* add comments and keep the previous selection

* optimizations + add redo feature

* linting

---------

Co-authored-by: Mr Simon C <iamontheinternet@yahoo.com>
Co-authored-by: shatfield4 <seanhatfield5@gmail.com>