checkSign function to check if a number is positive, negative or zero. The function should return "positive", "negative" or "zero".
checkSign should use multiple conditional operators
    testString: assert(/.+?\s*?\?\s*?.+?\s*?:\s*?.+?\s*?\?\s*?.+?\s*?:\s*?.+?/gi.test(code));
  - text: checkSign(10) should return "positive". Note that capitalization matters
    testString: assert(checkSign(10) === 'positive');
  - text: checkSign(-12) should return "negative". Note that capitalization matters
    testString: assert(checkSign(-12) === 'negative');
  - text: checkSign(0) should return "zero". Note that capitalization matters
    testString: assert(checkSign(0) === 'zero');
```