[e2e] Fix tests with page change

Because there are more (pseudo-)tab on the (page-)tab pabel, the tab for 
the first page is no longer visible and can't be clicked. By increasing 
the viewport width, it becomes visible again.

e2e/tests/e2e/button.spec.cy.ts

@@ -4,7 +4,9 @@ import {
 
 describe('Button element', { testIsolation: false }, () => {
   it('creates basic buttons in editor', () => {
+    cy.viewport(1280, 720); // if the screen is smaller the page tab won't be visible
     cy.openEditor();
+    cy.switchToTabbedViewMode();
     cy.wait(1000); // Wait for expansion panel to render. Otherwise the last panel is not there yet, sometimes.
     cy.contains('Sonstige').click();
     cy.contains('Knopf').click();