Test migration to jest by hand

Apparently using regular expressions is way easier.

test/isPrime/isPrime.js

@@ -0,0 +1,6 @@
+const isPrime = num => {
+const boundary = Math.floor(Math.sqrt(num));
+for (var i = 2; i <= boundary; i++) if (num % i === 0) return false;
+return num >= 2;
+};
+module.exports = isPrime;