[Summary] User study functionality

[nfelnlp]

• [x] Add a demonstration for users before they start the evaluation (using Selenium, automatic user questions, or screen recording)
• [x] Investigate how to run Flask application on a server, so we could access it via URL in a browser @OguzCennet
• [x] For "Feedback" option, check how to collect acceptability ratings in the user study (decide on rating values, save to files etc.)
• [x] Test sample interface ("Help me generate a question about...") with all operations
• [x] Check if the response time of all operations is not exceeding 60 seconds