Adding Cypress for e2e testing (#85)

* using the higher-level react-testing-library, and regenerating snapshot - renders real DOM elements
* Basic e2e testing with Cypress, following the guide here: https://www.gatsbyjs.com/docs/how-to/testing/end-to-end-testing/ ; needed to install cypress-local to avoid jest-cypress collision
* Adding accessibility testing support and basic a11y tests
* adding failure logging
* Adding nightly test run
* Fix misc stuff from lighthouse (#81)
* Removing local-cypress, relying instead on a combination
of type reference and eslint-plugin-cypress;
adding cypress to jest ignore paths to avoid conflict -
`npm test` is now jest-only, use `npm run test:e2e` to run cypress tests
* updating comment to clarify timezone

client/cypress/support/commands.js

@@ -0,0 +1,27 @@
+// ***********************************************
+// This example commands.js shows you how to
+// create various custom commands and overwrite
+// existing commands.
+//
+// For more comprehensive examples of custom
+// commands please read more here:
+// https://on.cypress.io/custom-commands
+// ***********************************************
+//
+//
+// -- This is a parent command --
+// Cypress.Commands.add('login', (email, password) => { ... })
+//
+//
+// -- This is a child command --
+// Cypress.Commands.add('drag', { prevSubject: 'element'},
+// (subject, options) => { ... })
+//
+//
+// -- This is a dual command --
+// Cypress.Commands.add('dismiss', { prevSubject: 'optional'},
+// (subject, options) => { ... })
+//
+//
+// -- This will overwrite an existing command --
+// Cypress.Commands.overwrite('visit', (originalFn, url, options) => { ... })