added the condition to handle negative integers for fastPowering algorithm.

[nikikalwar]

Issue:

Error:RangeError: Maximum call stack size exceeded #590

I have edited the fastpowering algorithm to handle negative integers and the test file to check the negative integers condition.

[JackyYin]

How about checking for power equals 1,
this can avoid from calculate fastPowering(base, 1) = fastPowering(base, 0) * fastPowering(base, 0) * base everytimes.

if (power === 0) {
  // Anything that is raised to the power of zero is 1.
  return 1;
}

if (power === 1) {
  return base;
}

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