Improve bufferToHex performance

[fabiospampinato]

The #7 method mentioned here is a good 10x faster compared to the one currently being used by this library.

That's the code:

// Pre-Init
const LUT_HEX_4b = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'];
const LUT_HEX_8b = new Array(0x100);
for (let n = 0; n < 0x100; n++) {
  LUT_HEX_8b[n] = `${LUT_HEX_4b[(n >>> 4) & 0xF]}${LUT_HEX_4b[n & 0xF]}`;
}
// End Pre-Init
function toHex(buffer) {
  let out = '';
  for (let idx = 0, edx = buffer.length; idx < edx; idx++) {
    out += LUT_HEX_8b[buffer[idx]];
  }
  return out;
}

Uppercase letters would need to be converted to lowercase though. And a Uint8Array needs to be passed to the function rather than an ArrayBuffer.

[fabiospampinato]

FWIW I've published a little module that does the conversion: https://www.npmjs.com/package/uint8-to-hex