Add iterative quick sort

[yavorski]

Hello,

Iterative quick sort is a popular interview question, so i think it would be nice to have it here.

[codecov]

Codecov Report

Merging #215 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #215   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files         143    144    +1     
  Lines        2556   2587   +31     
  Branches      422    427    +5     
=====================================
+ Hits         2556   2587   +31

Impacted Files	Coverage Δ
...lgorithms/sorting/quick-sort/QuickSortIterative.js	100% <100%> (ø)

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[appleJax]

Nice addition! Just to nitpick, it might be a little cleaner to store arrays on the stack. That way, each item in the stack corresponds to a single iteration.
e.g.

    let lowIndex = inputLowIndex;
    let highIndex = inputHighIndex;
    let partitionIndex;
    
    stack.push([ lowIndex, highIndex ]);

    while (!stack.isEmpty()) {
      [ lowIndex, highIndex ] = stack.pop();
      partitionIndex = partitionArray(lowIndex, highIndex);
      if (partitionIndex - 1 > lowIndex) {
        stack.push([ lowIndex, partitionIndex - 1 ]);
      }
      if (partitionIndex + 1 < highIndex) {
        stack.push([ partitionIndex + 1, highIndex ]);
      }
    }