Added WASD keys and speed variable

[mauro-miatello]

added WASD keys to move the snake and a variable SPEED to customize it to add different levels of difficulty in the future

[pjhades]

Hi, thanks for the PR! I like to have SPEED, but in terms of direction control, I'd like to keep the Vim style :)

[mauro-miatello]

de gustibus is not disputandum :)
so this is the reason for which I added also WASD combination
anyone can use the preferred keys, both works

[pjhades]

anyone can use the preferred keys, both works

Right. But I'd like to keep the Vim way. This repo started as merely a recreational thingy, where the Vim key bindings were supposed to make it more bizarre.