Reviewer chat cypress tests

This MR contains cypress test for the reviewer chat (related to #427 (closed)) . It checks the following actions:

1. Log in as editor.
2. Go to editor items and click on the item with status "Under Review".
3. Check that the "Reviewer chat" tab is visible.
4. Navigate to the "Reviewer chat" and verify the message displays correctly when no reviewer is selected (i.e., "No reviewer selected", "Select a reviewer to chat").
5. Invite a reviewer and then log in as a reviewer to accept the request.
6. Log back in as the editor and select the reviewer from the dropdown in the "Reviewer Chat" tab.
7. Verify that the message updates to "Chat to (reviewer name)", displaying the correct reviewer name.