Add Liu Hui's π algorithm

[mantou132]

https://en.wikipedia.org/wiki/Liu_Hui's_%CF%80_algorithm

e.g:

const getSideLength = (sideLength, count) => {
  if (count <= 0) return sideLength;
  const m = sideLength / 2;
  const g = Math.sqrt((0.5 ** 2) - (m ** 2));
  const j = 0.5 - g;
  return getSideLength(Math.sqrt((j ** 2) + (m ** 2)), count - 1);
};


const pi = (splitCount = 0) => {
  const sideLength = getSideLength(0.5, splitCount);
  const sideCount = 6 * (splitCount ? 2 ** splitCount : 1);
  return sideLength * sideCount;
};

// for (let i = 0; i < 100; i += 1) {
//   const p = pi(i);
//   console.log(i, p, p === Math.PI);
// }

export default pi;

[trekhleb]

Hi @mantou132 !
Thank you for suggestion! Would you please create a pull request for this algorithm?

[mantou132]

Submitted PR #61

[trekhleb]

Thank you @mantou132
The code is already in master.