Readline update, formatting and checks

Fix bugs in commands

Add commands in the commands directory

Update completion engine

context execution, error types refactors

feat: custom shell highlight (#50)

* no large gaps between prompts on empty input due to NewlineBefore and NewlineAfter

* removed lastLine placeholder

* don't print lastLine

* check firstRead in newlineAfter

* set lastLine every iteration

* custom ansi code for flag and command highlight color

* docstring