Function getBigSign

getBigSign(num): -1 | 0 | 1
Gets the sign of a number represented as a string, or bigint.
Parameters
- num: string | bigint
  {string | bigint} The number in string or bigint format to be used for deciding the sign.
Returns -1 | 0 | 1
0 if num is zero, 1 if num is positive, -1 if num is negative.