merge: WhileLoopFactorial: Optimize and add tests (#992)

* Optimised the factorial function.

There was previously an unnecessary check for if the number was 0 or 1.

* Create WhileLoopFactorial.test.js

The test was not present previously.

* result *= num

* Update WhileLoopFactorial.test.js

* testFactorial function

* Space for formatting.

* should fix the formatting issues. I was having trouble with npx standard, so I just used the online verifier at https://standardjs.com/demo.html

Maths/test/WhileLoopFactorial.test.js

@@ -0,0 +1,12 @@
+import { factorialize } from '../WhileLoopFactorial'
+
+function testFactorial (n, expected) {
+  test('Testing on ' + n + '!', () => {
+    expect(factorialize(n)).toBe(expected)
+  })
+}
+
+testFactorial(3, 6)
+testFactorial(7, 5040)
+testFactorial(0, 1)
+testFactorial(12, 479001600)