Added EulersTotientFunction function to the Maths Folder

Maths/test/EulersTotientFunction.test.js

@@ -0,0 +1,11 @@
+import { EulersTotientFunction } from '../EulersTotientFunction';
+
+describe('eulersTotientFunction', () => {
+  it('is a function', () => {
+    expect(typeof EulersTotientFunction).toEqual('function')
+  })
+  it('should return the phi of a given number', () => {
+    const phiOfNumber = EulersTotientFunction(10)
+    expect(phiOfNumber).toBe(4)
+  })
+})