Create a function that will build a staircase using the underscore _ and hash # symbols. A positive value denotes the staircase's upward direction and downwards for a negative value.
staircase(3) ➞ "__#\n_##\n###"
__#
_##
###
staircase(7) ➞ "______#\n_____##\n____###\n___####\n__#####\n_######\n#######"
______#
_____##
____###
___####
__#####
_######
#######
staircase(2) ➞ "_#\n##"
_#
##
staircase(-8) ➞ "########\n_#######\n__######\n___#####\n____####\n_____###\n______##\n_______#"
########
_#######
__######
___#####
____####
_____###
______##
_______#
\n).