Add mostPerformant snippet

snippets/mostPerformant.md

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+### mostPerformant
+
+Returns the index of the function in an array of functions which executed the fastest.
+
+Use `Array.map()` to generate an array where each value is the total time taken to execute the function
+after `iterations` times. Use the difference in `performance.now()` values before and after to get the total time
+in milliseconds to a high degree of accuracy.
+Use `Math.min()` to find the minimum execution time, and return the index of that shortest time which
+corresponds to the index of the most performant function. Omit the second argument, `iterations`, to use a default of 10,000 iterations. The more iterations, the more reliable the result but the longer it will take.
+
+```js
+const mostPerformant = (fns, iterations = 10000) => {
+  const times = fns.map(fn => {
+    const before = performance.now();
+    for (let i = 0; i < iterations; i++) fn();
+    return performance.now() - before;
+  });
+  return times.indexOf(Math.min(...times));
+};
+```
+
+```js
+mostPerformant([
+  () => {
+    // Loops through the entire array before returning `false`
+    [1, 2, 3, 4, 5, 6, 7, 8, 9, '10'].every(el => typeof el === 'number')
+  },
+  () => {
+    // Only needs to reach index `1` before returning false
+    [1, '2', 3, 4, 5, 6, 7, 8, 9, 10].every(el => typeof el === 'number')
+  }
+]); // 1
+```