Add info to README for how to run the fuzzer

[jasikpark]

It was unclear how to run the fuzzer - I eventually figured out it should be compiled with tsc and run with node:

import { chunkStringIntoFours } from "../src/chunkStringIntoFours";

function chunkStringIntoFoursForLoop(input: string): string {
  if (typeof input !== "string") {
    throw Error("chunkStringIntoFours can only chunk strings");
  }
  if (/[\uD800-\uDBFF]/.test(input)) {
    throw Error("chunkStringIntoFours does not support non BMP strings");
  }
  if (/[\r\n]/.test(input)) {
    throw Error("chunkStringIntoFours does not support whitespace");
  }

  const array = [];

  // make input.length / 4 strings that contain 4 characters
  for (let i = 0; i < input.length; i++) {
    if (i % 4 === 0) {
      array[Math.floor(i / 4)] = input[i];
    } else {
      array[Math.floor(i / 4)] += input[i];
    }
  }

  return array.join(" ");
}

import { fuzz } from "fuzzing";

const errors = fuzz((input) => {
  try {
    if (chunkStringIntoFours(input) !== chunkStringIntoFoursForLoop(input)) {
        throw Error("chunkStringIntoFours did not output the same as chunkStringIntoFoursForLoop");
    }
  } catch (e: unknown) {
    if (
      e instanceof Error &&
      ["chunkStringIntoFours can only chunk strings"].includes(e.message)
    ) {
      // no error
      return true;
    }

    throw e;
  }
})
  .string()
  .errors();

console.log(errors);

Example script that I made that imports the function to be tested and then I have an npm script:

{
	"scripts": {
		"fuzz": "tsc --incremental && node ./dist/fuzz/chunkStringIntoFours.js",
	}
}