Added jest, jest-puppeteer and jest-image-snapshot for e2e tests

e2e/spec/flowchart.spec.js

@@ -0,0 +1,10 @@
+/* eslint-env jest */
+describe('Google', () => {
+  beforeAll(async () => {
+    await page.goto('https://google.com')
+  })
+
+  it('should be titled "Google"', async () => {
+    await expect(page.title()).resolves.toMatch('Google')
+  })
+})