test: Add test for CORS

cypress/integration/cors_spec.js

@@ -0,0 +1,9 @@
+describe('cross domain images with liberal CORS policy', function() {
+    it('load', function() {
+        cy.visit('http://localhost:8080/cypress/test-pages/cors.html');
+        cy.get('#result').should(($el) => {
+            const count = $el.text().split(',').length
+            expect(count).to.equal(3);
+        });
+    })
+});