merge: Add project-euler problem 12 (#767)

* Add project-euler problem 12

* Fix raised alert in problem 12

* Fixed for loop in Problem012

* fix alerts in Problem012

* Update Problem012

Project-Euler/test/Problem012.test.js

@@ -0,0 +1,8 @@
+import { firstTriangularWith500Divisors } from '../Problem012'
+
+describe('checkFirstTriangularWith500Divisors()', () => {
+  it('Problem Statement Answer', () => {
+    const firstTriangular = firstTriangularWith500Divisors()
+    expect(firstTriangular).toBe(76576500)
+  })
+})