Add test for Rollbar logging on the website (#2320)

* Add test for Rollbar logging on the website

* Move `rollbar.cy.js` test file to `integration` folder

site/gatsby-site/cypress/e2e/integration/rollbar.cy.js

@@ -0,0 +1,19 @@
+describe('Rollbar', () => {
+  it('Should log an error to Rollbar', () => {
+    cy.intercept('POST', 'https://api.rollbar.com/api/1/item/').as('rollbarAPICall');
+
+    cy.visit('/login');
+
+    cy.get('input[name=email]').type(Cypress.env('e2eUsername'));
+
+    cy.get('input[name=password]').type('invalidPassword');
+
+    cy.get('[data-cy="login-btn"]').click();
+
+    cy.wait('@rollbarAPICall').then((interception) => {
+      expect(interception.response.statusCode).to.equal(200);
+      expect(interception.response.statusMessage).to.equal('OK');
+      expect(interception.response.body.err).to.equal(0);
+    });
+  });
+});