Add basic accessibility scan for most public pages. Disable any a11y tests with known issues

cypress/integration/header.spec.ts

@@ -0,0 +1,18 @@
+describe('Header', () => {
+    it('should pass accessibility tests', () => {
+        cy.visit('/');
+        cy.injectAxe();
+
+        // Header must first be visible
+        cy.get('ds-header').should('be.visible');
+
+        // Analyze <ds-header> for accessibility
+        cy.checkA11y({
+            include: ['ds-header'],
+            exclude: [
+                ['#search-navbar-container'], // search in navbar has duplicative ID. Will be fixed in #1174
+                ['.dropdownLogin']            // "Log in" link has color contrast issues. Will be fixed in #1149
+            ],
+        });
+    });
+});