Splice(-1, 0, “thing”) should append

Right now, List(1,2,3).Splice(-1, 0, "thing") returns List(1, 2, "thing", 3)

It should instead return List(1, 2, 3, "thing")

See List(1,2,3).Splice(0, 0, List(4)) should return List(1,2,3,4) - #10 by Christian_Rodriguez3

With this rule, if you want to delete the last item in a list, you should do MyList.Splice(-2, 1)