A simple Chip8 emulator inspired from Tobias V. Langhoff blog post.
The keyboard keys are mapped as described in this comment:
/**
* Mapping from (qwerty)
*
* 1 2 3 4
* q w e r
* a s d f
* z x c v
*
* to (chip-8)
*
* 1 2 3 C
* 4 5 6 D
* 7 8 9 E
* A 0 B F
*
*/