The BS key is used to delete the character on the left of the cursor.
The DEL key is used to delete the character on the right of the cursor.
BackSpace was already implemented. This CL implements DEL.
This is related to bug:
https://github.com/ArthurSonzogni/FTXUI/issues/4
Most CJK users use IME (input method) to type CJK characters. They need
the cursor to be at the correct location, not in the bottom right
corner.
This CL does:
* Move the cursor the focus() element.
* Hide the cursor (and show it at exit)
* Intercept SIGINT to guarantee proper cleanup all the time.
This should fix the second issue mentionned on:
https://github.com/ArthurSonzogni/FTXUI/issues/2
