arrow key support

[Quicksilver151]

being on a laptop makes it hard to use h,j,k,l keys without the touchpad getting in the way, so arrow keys are preferable for me. would it be possible to allow cursor to move with arrow keys instead?

[zeckrust]

Hey! I added these lines in the cursor.gd file, under the _input(event) function on line 87. It seems to be working. I didn't get any issues but I have not tested it that much.

	if Input.is_key_pressed(KEY_UP):
		move_line(-1)
		accept_event()
	if Input.is_key_pressed(KEY_DOWN):
		move_line(+1)
		accept_event()
	if Input.is_key_pressed(KEY_LEFT):
		move_column(-1)
		accept_event()
	if Input.is_key_pressed(KEY_RIGHT):
		move_column(+1)
		accept_event()